Cell Biology Exam 1

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A group of membrane proteins can be extracted from membranes only by using detergents. All the proteins in this group have a similar amino acid sequence at their C-terminus: -KKKKKXXC (where K stands for lysine, X stands for any amino acid, and C stands for cysteine). This sequence is essential for their attachment to the membrane. What is the most likely way in which the C-terminal sequence attaches these proteins to the membrane? (a) The cysteine residue is covalently attached to a membrane lipid. (b) The peptide spans the membrane as an α helix. (c) The peptide spans the membrane as part of a β sheet. (d) The positively charged lysine residues interact with an acidic integral membrane protein.

(a)

Consider the apical location of a particular protein expressed in epithelial cells, illustrated in Figure Q11-50A. When a molecule that chelates calcium is added to the cell culture medium, you observe a redistribution of that protein around the entire cell, shown in Figure Q11-50B. Which is most likely to be true about the role of calcium in maintaining an apical distribution of protein A? (a) calcium is required to maintain the structural integrity of the junctional complex (b) calcium is required for the binding of the junctional proteins to the cell cortex (c) calcium is a structural component of protein A (d) calcium inhibits intracellular transport of protein A

(a)

Membrane lipids are capable of many different types of movement. Which of these does not occur spontaneously in biological membranes? (a) switching between lipid layers (b) lateral movement (c) rotation (d) flexing of hydrocarbon chains

(a)

Membrane synthesis in the cell requires the regulation of growth for both halves of the bilayer and the selective retention of certain types of lipids on one side or the other. Which group of enzymes accomplishes both of these tasks? (a) flippases (b) phospholipases (c) convertases (d) glycosylases

(a)

Most animal fats form a solid at room temperature, while plant fats remain liquid at room temperature. Which of the following is a feature of lipids in plant membranes that best explains this difference? (a) unsaturated hydrocarbons (b) longer hydrocarbon tails (c) higher levels of sterols (d) larger head groups

(a)

Plasma membranes are extremely thin and fragile, requiring an extensive support network of fibrous proteins. This network is called the ____________. (a) cortex. (b) attachment complex. (c) cytoskeleton. (d) spectrin.

(a)

Porin proteins form large, barrel-like channels in the membrane. Which of the following is not true about these channels? (a) They are made primarily of α helices. (b) They are made primarily of β sheets. (c) They cannot form narrow channels. (d) They have alternating hydrophobic and hydrophilic amino acids.

(a)

The endothelial cells found closest to the site of an infection express proteins called lectins. Each lectin binds to a particular ____________ that is presented on the surface of a target cell. (a) oligosaccharide (b) aminophospholipid (c) polysaccharide (d) sphingolipid

(a)

The lateral movement of transmembrane proteins can be restricted by several different mechanisms. Which mechanism best describes the process by which a budding yeast cell designates the site of new bud formation during cell division? (a) proteins are tethered to the cell cortex (b) proteins are tethered to the extracellular matrix (c) proteins are tethered to the proteins on the surface of another cell (d) protein movement is limited by the presence of a diffusion barrier

(a)

Water molecules readily form hydrogen bonds with other polar molecules, and when they encounter nonpolar molecules they must form hydrogen-bonding networks with neighboring water molecules. Which of the following molecules will cause a "cage" of water to form? (a) 2-methylpropane (b) acetone (c) methanol (d) urea

(a)

Which of the following phenomena will be observed if a cell's membrane is pierced? (a) the membrane reseals (b) the membrane collapses (c) a tear is formed (d) the membrane expands

(a)

Which of the following phospholipid precursors is the most hydrophobic? (a) triacylglycerol (b) diacylglycerol (c) phosphate (d) glycerol

(a)

Which type of lipids are the most abundant in the plasma membrane? (a) phospholipids (b) glycolipids (c) sterols (d) triacylglycerides

(a)

Table Q2-23 indicates the electrons in the first four atomic electron shells for selected elements. On the basis of the information in the chart and what you know about atomic structure, which elements form stable but reactive diatomic gases? Table Q2-23 (a) nitrogen, oxygen (b) helium, neon (c) sodium, potassium (d) magnesium, calcium

(a) An oxygen atom with six outer electrons needs two more to attain a stable outer shell. This can be achieved by forming two covalent bonds with a second oxygen, as shown on the right. Similarly, a nitrogen atom needs three more electrons and makes three covalent bonds with another nitrogen atom.

Which of the following are examples of isomers? (a) glucose and galactose (b) alanine and glycine (c) adenine and guanine (d) glycogen and cellulose

(a) Glucose and galactose are both six-carbon sugars and thus both have the formula C6H12O6. They are therefore isomers of each other. Adenine and guanine are bases containing different numbers of nitrogen and oxygen atoms. Glycogen and cellulose are different polymers of glucose. Alanine and glycine are amino acids with quite different side chains: a methyl group and a hydrogen atom, respectively.

Which of the following elements is least abundant in living organisms? (a) sulfur (b) carbon (c) oxygen (d) nitrogen

(a) Sulfur is the least abundant element among the choices given.

Larger molecules have hydrogen-bonding networks that contribute to specific, high-affinity binding. Smaller molecules such as urea can also form these networks. How many hydrogen bonds can urea (Figure Q2-36) form if dissolved in water? Figure Q2-36 (a) 6 (b) 5 (c) 3 (d) 4

(a) Urea can form at least six hydrogen bonds in water: two from the oxygen atom and one from each hydrogen atom.

You have isolated two mutants of a normally pear-shaped microorganism that have lost their distinctive shape and are now round. One of the mutants has a defect in a protein you call A and the other has a defect in a protein you call B. First, you grind up each type of mutant cell and normal cells separately and separate the plasma membranes from the cytoplasm, forming the first cell extract. Then you set aside a portion of each fraction for later testing. Next, you wash the remaining portion of the membrane fractions with a low concentration of urea (which will unfold proteins and disrupt their ability to interact with other proteins) and centrifuge the mixture. The membranes and their constituent proteins form a pellet, and the proteins liberated from the membranes by the urea wash remain in the supernatant. When you check each of the fractions for the presence of A or B, you obtain the results given below. Which of the following statements are consistent with your results (more than one answer may apply)? (a) Protein A is an integral membrane protein that interacts with B, a peripheral membrane protein that is part of the cell cortex. (b) Protein B is an integral membrane protein that interacts with A, a peripheral membrane protein that is part of the cell cortex. (c) Proteins A and B are both integral membrane proteins. (d) The mutation in A affects its ability to interact with B.

(a) and (d) The results from the extracts of normal cells show that protein A is an integral membrane protein that remains in the membrane through all the treatments, whereas protein B is a peripheral membrane protein that can be removed from the membrane by urea. In the cell extracts from the mutants with a defect in A, the A protein still remains in the membrane, but the B protein does not. This is consistent with the mutation in A affecting its interaction with B. The same results are obtained when the B protein is mutant, which is consistent with the idea that A and B interact. The loss of an interaction between an integral membrane protein and a protein in the cortex would be more likely to result in a change in cell shape than the loss of an interaction between an integral membrane protein and a protein on the exterior of the cell.

A bacterium is suddenly expelled from a warm human intestine into the cold world outside. Which of the following adjustments might the bacterium make to maintain the same level of membrane fluidity? (a) Produce lipids with hydrocarbon tails that are longer and have fewer double bonds. (b) Produce lipids with hydrocarbon tails that are shorter and have more double bonds. (c) Decrease the amount of cholesterol in the membrane. (d) Decrease the amount of glycolipids in the membrane.

(b)

Consider the apical location of a particular protein expressed in epithelial cells, illustrated in Figure Q11-49A. Which type of defect described below is the most likely to cause the redistribution of that protein around the entire cell, shown in Figure Q11-49B? (a) a nonfunctional protein glycosylase (b) the deletion of a junctional protein (c) the truncation of a protein found in the extracellular matrix (d) a nonfunctional flippase

(b)

Formation of a lipid bilayer is energetically favorable. How does this arrangement result in higher entropy for the system, and thus make bilayer formation energetically favorable? (a) Polar head groups form a hydrogen-bonding network at the interface with water. (b) Water molecules form cagelike structures around hydrophobic molecules. (c) Hydrogen bonds form between neighboring polar head groups in the bilayer. (d) Fatty acid tails are highly saturated and flexible.

(b)

In the photosynthetic archaean Halobacterium halobium, a membrane transport protein called bacteriorhodopsin captures energy from sunlight and uses it to pump protons out of the cell. The resulting proton gradient serves as an energy store that can later be tapped to generate ATP. Which statement best describes how bacteriorhodopsin operates? (a) The absorption of sunlight triggers a contraction of the β barrel that acts as the protein's central channel, squeezing a proton out of the cell. (b) The absorption of sunlight triggers a shift in the conformation of the protein's seven, membrane spanning α helices, allowing a proton to leave the cell. (c) The absorption of sunlight triggers a restructuring of bacteriorhodopsin's otherwise unstructured core to form the channel through which a proton can exit the cell. (d) The absorption of sunlight triggers the activation of an enzyme that generates ATP.

(b)

Membrane proteins, like membrane lipids, can move laterally by exchanging positions with other membrane components. Which type of membrane proteins is expected to be the least mobile, based on their function? (a) channels (b) anchors (c) receptors (d) enzymes

(b)

The lateral movement of transmembrane proteins can be restricted by several different mechanisms. Which mechanism best describes the process by which focal adhesions are formed to promote cell motility? (a) proteins are tethered to the cell cortex (b) proteins are tethered to the extracellular matrix (c) proteins are tethered to the proteins on the surface of another cell (d) protein movement is limited by the presence of a diffusion barrier

(b)

The plasma membrane serves many functions, many of which depend on the presence of specialized membrane proteins. Which of the following roles of the plasma membrane could still occur if the bilayer were lacking these proteins? (a) intercellular communication (b) selective permeability (c) cellular movement (d) import/export of molecules

(b)

There are two properties of phospholipids that affect how tightly they pack together: the length of the hydrocarbon chain and the number of double bonds. The degree of packing, in turn, influences the relative mobility of these molecules in the membrane. Which of the following would yield the most highly mobile phospholipid (listed as number of carbons and number of double bonds, respectively)? (a) 24 carbons with 1 double bond (b) 15 carbons with 2 double bonds (c) 20 carbons with 2 double bonds (d) 16 carbons with no double bonds

(b)

We know the detailed molecular structure and mechanism of action of the transmembrane protein bacteriorhodopsin. This protein uses sunlight as the source of energy to pump ______ out of the cell. (a) ATP (b) H+ (c) K+ (d) Na+

(b)

Where does most new membrane synthesis take place in a eukaryotic cell? (a) in the Golgi apparatus (b) in the endoplasmic reticulum (c) in the plasma membrane (d) in the mitochondria (e) on ribosomes

(b)

It is possible to follow the movement of a single molecule or a small group of molecules. This requires the use of antibodies linked to small particles of gold, which appear as dark spots when tracked through video microscopy. What is this method called? What does the abbreviation stand for? (a) SDS (b) SPT (c) GFP (d) FRAP

(b), single-particle tracking

Both glycoproteins and proteoglycans contribute to the carbohydrate layer on the surface of the cell. Which of the following is not true of glycoproteins? (a) They can be secreted into the extracellular environment. (b) They have only one transmembrane domain. (c) They have long carbohydrate chains. (d) They are recognized by lectins.

(c)

New membrane phospholipids are synthesized by enzymes bound to the _____________ side of the _________________ membrane. (a) cytosolic, mitochondrial (b) luminal, Golgi (c) cytosolic, endoplasmic reticulum (d) extracellular, plasma

(c)

The lateral movement of transmembrane proteins can be restricted by several different mechanisms. Which mechanism best describes the process by which neutrophils are recruited by endothelial cells? (a) proteins are tethered to the cell cortex (b) proteins are tethered to the extracellular matrix (c) proteins are tethered to the proteins on the surface of another cell (d) protein movement is limited by the presence of a diffusion barrier

(c)

The lateral movement of transmembrane proteins can be restricted by several different mechanisms. Which mechanism best describes the process by which an antigen-presenting cell triggers an adaptive immune response? (a) proteins are tethered to the cell cortex (b) proteins are tethered to the extracellular matrix (c) proteins are tethered to the proteins on the surface of another cell (d) protein movement is limited by the presence of a diffusion barrier

(c)

Three phospholipids X, Y, and Z are distributed in the plasma membrane as indicated in Figure Q11-14. For which of these phospholipids does a flippase probably exist? Figure Q11-14 (a) X only (b) Z only (c) X and Y (d) Y and Z

(c)

Unlike soluble, cytosolic proteins, membrane proteins are more difficult to purify. Which of the following substances is most commonly used to help purify a membrane protein? (a) high salt solution (b) sucrose (c) detergent (d) ethanol

(c)

Which of the following statements is true? (a) Phospholipids will spontaneously form liposomes in nonpolar solvents. (b) In eukaryotes, all membrane-enclosed organelles are surrounded by one lipid bilayer. (c) Membrane lipids diffuse within the plane of the membrane. (d) Membrane lipids frequently flip-flop between one monolayer and the other.

(c) The remaining answers are false. Phospholipids form bilayers only in polar solvents. Nuclei and mitochondria are enclosed by two membranes. Membrane lipids rarely flip- flop between one monolayer and the other.

Which of the following statements about the carbohydrate coating of the cell surface is false? (a) It is not usually found on the cytosolic side of the membrane. (b) It can play a role in cell-cell adhesion. (c) The arrangement of the oligosaccharide side chains is highly ordered, much like the peptide bonds of a polypeptide chain. (d) Specific oligosaccharides can be involved in cell-cell recognition.

(c) The sugars in an oligosaccharide side chain attached to the cell surface can be joined together in many different ways and in varied sequences.

Most types of molecules in the cell have asymmetric (chiral) carbons. Consequently there is the potential to have two different molecules that look much the same but are mirror images of each other and therefore not equivalent. These special types of isomer are called stereoisomers. Which of the four carbons circled in Figure Q2-51 is the asymmetric carbon that determines whether the amino acid (threonine in this case) is a ᴅ or an ʟ stereoisomer? Figure Q2-51 (a) 1 (b) 2 (c) 3 (d) 4

(c) Two of the carbon atoms of threonine are asymmetric (numbered 2 and 3 in Figure Q2-51) but by convention it is the α-carbon (number 3) that determines whether the amino acid is the ᴅ or ʟ isomer.

Membranes undergo spontaneous rearrangement if torn. Which of the following would happen if a cell membrane had a large tear? Figure 11-17

Cholesterol serves several essential functions in mammalian cells. Which of the following is not influenced by cholesterol? (a) membrane permeability (b) membrane fluidity (c) membrane rigidity (d) membrane thickness

(d)

Diversity among the oligosaccharide chains found in the carbohydrate coating of the cell surface can be achieved in which of the following ways? (a) varying the types of sugar monomers used (b) varying the types of linkages between sugars (c) varying the number of branches in the chain (d) all of the above

(d)

Macromolecules in the cell can often interact transiently as a result of noncovalent interactions. These weak interactions also produce stable, highly specific interactions between molecules. Which of the factors below is the most significant in determining whether the interaction will be transient or stable? (a) the size of each molecule (b) the concentration of each molecule (c) the rate of synthesis (d) surface complementarity between molecules

(d)

Membrane curvature is influenced by the differential lipid composition of the two membrane monolayers. Which factor do you think has the largest impact on the curvature of biological membranes? (a) amount of cholesterol (b) charge of the lipid head group (c) length of the hydrocarbon tails (d) size of the lipid head group

(d)

Red blood cells have been very useful in the study of membranes and the protein components that provide structural support. Which of the following proteins is the principal fibrous protein in the cortex of the red blood cell? (a) tubulin (b) attachment proteins (c) actin (d) spectrin

(d)

Select the answer that best completes the following statement: Chemical reactions in living systems occur in an ____________ environment, within a narrow range of temperatures. (a) optimal (b) organic (c) extracellular (d) aqueous

(d)

Some lipases are able to cleave the covalent bonds between the glycerol backbone and the attached fatty acid. What final products do you expect to accumulate through the action of the enzyme monoacylglycerol lipase? (a) phosphoglycerol and free fatty acid (b) sterol and glycerol (c) free phosphate and glycerol (d) glycerol and free fatty acid

(d)

The lateral movement of transmembrane proteins can be restricted by several different mechanisms. Which mechanism best describes the process by which nutrients are taken up at the apical surface of the epithelial cells that line the gut and released from their basal and lateral surfaces? (a) proteins are tethered to the cell cortex (b) proteins are tethered to the extracellular matrix (c) proteins are tethered to the proteins on the surface of another cell (d) protein movement is limited by the presence of a diffusion barrier

(d)

Which of the following membrane lipids does not contain a fatty acid tail? (a) phosphatidylcholine (b) a glycolipid (c) phosphatidylserine (d) cholesterol

(d)

We can estimate the relative mobility of a population of molecules along the surface of a living cell by fluorescently labeling the molecules of interest, bleaching the label in one small area, and then measuring the speed of signal recovery as molecules migrate back into the bleached area. What is this method called? What does the abbreviation stand for? (a) SDS (b) SPT (c) GFP (d) FRAP

(d), fluorescence recovery after photobleaching

A folded protein structure with which free-energy (G) value would likely have the most stable conformation?

1 FEEDBACK: Free energy is designated by the letter G. If the free-energy value decreases during protein folding, the reaction is energetically favorable. Proteins generally fold along the most energetically favorable pathway, so the conformation with the lowest free-energy (G) value, 1, is the correct answer.

Glycolysis alone captures approximately what percentage of the free energy available in a molecule of glucose?

10%

On the phospholipid molecule in Figure Q2-53, label each numbered line with the correct term selected from the list below. Figure Q2-53

1—D; 2—A; 3—C; 4—J; 5—I; 6—H; 7—E

The number of ATP molecules that could be synthesized from the energy released by the transfer of two electrons from NADH to molecular oxygen is ___.

2.5

Which of the following describes the chromosomes makeup of a somatic cell of a human biological male

22 pairs of autosomes + 1 X chromosomes +1 Y chromosomes

Shown is the structure of a mitochondrion with different compartments labeled. Which of the numbers represents the most permeable membrane of the mitochondrion?

30. Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. DNA molecules, like proteins, consist of a single, long polymeric chain that is assembled from small monomeric subunits. B. The polarity of a DNA strand results from the polarity of the nucleotide subunits. C. There are five different nucleotides that become incorporated into a DNA strand. D. Hydrogen bonds between each nucleotide hold individual DNA strands together.

30. A. False. DNA is double-stranded. It is actually is made of two polymers that are complementary in sequence. B. True. C. False. There are four different nucleotides that are used to make a DNA polymer: adenine, thymine, guanine, and cytosine. A fifth nucleotide, uracil, is found exclusively in RNA molecules, replacing thymine nucleotides in the DNA sequence. D. False. Nucleotides are linked covalently through phosphodiester bonds. Hydrogen- bonding between nucleotides from opposite strands holds the DNA molecule together.

32. For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below. Not all words or phrases will be used; each word or phrase should be used only once. In eucaryotic __________________, DNA is complexed with proteins to form __________________. The paternal and maternal copies of human Chromosome 1 are __________________, whereas the paternal copy of Chromosome 1 and the maternal copy of Chromosome 3 are __________________. Cytogeneticists can determine large-scale chromosomal abnormalities by looking at a patient's __________________. Fluorescent molecules can be used to paint a chromosome by a technique that employs DNA ______________, and thereby to identify each chromosome by microscopy. bands chromatin chromosomes condensation extended kinetochore homologous nonhomologous hybridization karyotype

32. chromosome, chromatin, homologous, nonhomologous, karyotype, hybridization

37. For each of the following sentences, choose one of the options enclosed in square brackets to make a correct statement about nucleosomes. A. Nucleosomes are present in [procaryotic/eucaryotic] chromosomes, but not in [procaryotic/eucaryotic] chromosomes. B. A nucleosome contains two molecules each of histones [H1 and H2A/H2A and H2B] as well as of histones H3 and H4. C. A nucleosome core particle contains a core of histone with DNA wrapped around it approximately [twice/three times/four times]. D. Nucleosomes are aided in their formation by the high proportion of [acidic/basic/polar] amino acids in histone proteins. E. Nucleosome formation compacts the DNA into approximately [one- third/one-hundredth/one-thousandth] of its original length.

37. A: eucaryotic, procaryotic. B: H2A and H2B. C: twice. D: basic. E: one-third

Export of RNA from the nucleus requires the RNA to have which characteristic(s)?

5' cap and poly-A tail

The sequence of the coding strand of a DNA molecule (that is, the DNA strand that contains the codons specifying the protein sequence) is 5'-CGGATGCTTA-3'. What is the sequence of the RNA made from this DNA?

5'-CGGAUGCUUA-3'

The pH of the mitochondrial matrix is ___________, which is ___________ than that of the intermembrane space.

7.9; higher

A mutation in the ___________ of the gene encoding the enzyme lactase enables expression of this gene in adults. A. regulatory sequence B. coding sequence C. exon D. intron

A transcriptional regulator that activates expression of additional transcriptional regulators that induce production of a particular cell type or organ is called a A. master regulator. B. reprogramming regulator. C. feedback activator. D. terminal differentiator.

An open reading frame (ORF) is defined as a sequence that has about 100 codons that lack stop codons. Why is finding ORFs helpful in determining the gene number in an unknown sequence? A. A random sequence is expected have a stop codon every 20 codons. B. Stop codons are subject to positive selection and are very frequent. C. Open reading frames are always genes that are expressed. D. Open reading frames never occur randomly.

DNA is a better molecule for long-term storage of genetic information than RNA because A. the deoxyribose sugar stabilizes DNA chains. B. the uracil in DNA is less easily mutated. C. DNA is able to make complex folded secondary structures. D. DNA is able to autocatalyze its own repair.

Excess amounts of the amino acid tryptophan result in downregulation of the expression of the enzymes required for its synthesis due to A. the repressor binding to the operator. B. inactivation of the repressor protein. C. the inability of the repressor to bind to the operator. D. the inactivation of RNA polymerase.

Generally, bacterial promoters that are regulated by transcriptional activators bind ___________ to RNA polymerase on their own, but promoters that are regulated with transcriptional repressors bind ___________ to RNA polymerase. A. weakly; strongly B. strongly; weakly C. weakly; weakly D. strongly; strongly

Heterochromatin can spread along a chromosome until it encounters a A. barrier DNA sequence. B. heterochromatin-specific protein. C. histone modifying enzyme. D. unmodified histone tail.

How are the primers from which DNA synthesis starts different from the DNA itself? A. The primers are made up of RNA not DNA. B. The primers are not properly based paired so they can be removed. C. The primers have three phosphates on each nucleotide. D. The primers do not have a 3′ −OH.

How do tRNAs become attached to the correct amino acid? A. aminoacyl-tRNA synthetases B. RNA polymerases C. rRNA ribozymes D. translation initiation factors

If lactose and glucose are both available to a bacterial cell, which carbon source(s) will be used? A. glucose B. lactose C. both lactose and glucose D. cyclic AMP

In the cell, enhancer sequence functions are limited in their range of action by the formation of ___________ that hold specific genes and enhancers in close proximity. A. loops B. chromatin C. helices D. operons

In which direction, and on which strands does DNA replication proceed from a replication origin on a chromosome? A. in both directions, on both strands B. only on one strand in the 5′ à 3′ direction C. only on one strand in the 3′ à 5′ direction D. from the left to the right, on both strands

Long noncoding RNA (lncRNA) can function as a(n) A. protein scaffold. B. RNA polymerase. C.transcriptional regulator. D. telomerase.

Meselson and Stahl performed a classic experiment to explore three models for the mechanism of DNA replication. Which of the models held that the two parental strands would remain associated after replication? A. conservative B. semiconservative C. dispersive D. liberal

MicroRNAs block the expression of a specific gene product by binding to the ___________ and inhibiting ___________. A. mRNA; translation B. DNA; transcription C. protein; activity D. ribosome; translation

Mobile genetic elements can promote gene duplication and exon shuffling by A. serving as targets for homologous recombination. B. inserting into an exon and destroying its function. C. excising themselves from a gene. D. replicating genes during the mobilization process.

RNA sequencing can give a more accurate estimate of the number of genes in a genome than finding ORFs can because A. RNA sequencing can rule out potential ORFs that are not transcribed. B. RNA sequencing is more accurate than DNA sequencing. C. RNA sequencing always includes introns. D. RNA sequencing will not identify genes for functional or regulatory RNA.

Shown below is the end of a newly replicated chromosome. Which strand will telomerase elongate? A.the template of lagging strand B. the incomplete newly synthesized lagging strand C. both strands D. neither of the strands, this is done by polymerase

Single nucleotide changes from unrepaired DNA damage that lead to uncontrolled cell division can lead to which of the following conditions? A. cancer B. sickle cell anemia C. cell death D. aging

The bonds that link two DNA strands together are A. hydrogen bonds. B. electrostatic interactions. C. phosphodiester bonds. D. phosphoanhydride bonds.

The catalytic sites for peptide bond formation during translation is found in which part of the ribosome? A. large subunit RNAs B. large subunit proteins C. small subunit RNAs D. small subunit proteins

The conservation of the organization of a region of a chromosome between species—that is, all of the genes in the same order in that region—is called A. conserved synteny. B. conserved sequence. C. phylogenetic. D. purified sequence.

The consistent diameter of the DNA double helix arises because of which property? A. base pairing of pyrimidines with purines B. the use of deoxyribose sugar with a 3′ -OH C. phosphodiester linkages having a consistent bond length D. the antiparallel nature of the two strands of DNA

The control of a gene product's levels or activity after transcription has taken place is called A. post-transcriptional control. B. cell memory. C. combinatorial control. D. epigenetic inheritance.

The energy for the polymerization reaction in DNA synthesis is powered by A. the breaking of high-energy phosphate bonds in the deoxynucleotides. B. the formation of the phosphodiester bonds between nucleotides. C. the breaking of the hydrogen bonds between complementary base pairs. D. the association/disassociation cycles of the DNA polymerase enzyme.

The part of the DNA molecule that carries the information for producing proteins is A. the order of the nucleotide bases. B. the sequence of the deoxyribose sugar groups. C. the 3′ hydroxyl terminus. D. the phosphate groups at the 5′ end.

The percentage of human DNA that is in protein-coding exon sequences is ___________ compared to the percentage of human DNA that is in repetitive elements, including mobile genetic elements, which is ___________. A. 1.5%; 50% B. 3%; 10% C. 10%; 50% D. 50%; 1.5%

The process of gene expression always involves which process(es) described in the central dogma? A. transcription B. translation C. replication D. transcription and translation

The reading frame to use for translating an mRNA into functional protein is determined by the A. location of an AUG. B. promoter sequence. C. 5′ cap. D. replication origin.

The sequence at which DNA replication begins tends to have which characteristic? A. AT-rich B. A-rich C. G-rich D. GC-rich

The splicing of introns out of an mRNA molecule is catalyzed by A. RNA molecules that base pair with the splice sites to promote intron removal. B. proteins that contain metal ions to pull electrons from the phosphate bonds. C. RNA molecules that act as a template for new RNA synthesis using exons only. D. proteins that act as nucleases to chew away and remove the introns.

The total size of the human genome is approximately ___________ base pairs. A. 3.2 billion B. 3.2 million C. 3,200 D. 30,000

Using the technique shown below, Meselson and Stahl did an experiment where they grew cells in heavy medium for many generations, then after a single generation in light medium, they observed a single band of intermediate weight after centrifugation. This experiment ruled out which model of DNA replication? A. conservative B. semiconservative C. dispersive D. liberal

What can happen if heterochromatin spreads inappropriately into an area with active genes? A.The active genes can become silenced. B. Heterochromatin cannot spread into areas with active genes. C. The genes will resist and remain active. D. The region will convert into a telomere.

What is the benefit of protein synthesis in polyribosomes? A. More protein can be produced from a single RNA. B. Protein translation is more accurate. C. Ribosomes can stay in the nucleus. D. Uncharged tRNAs can be used.

What is the first step that must occur to repair damage on one strand of the double helix? A. The damaged region must be removed. B. The gap caused by the damage must be filled. C. The DNA backbone must be sealed. D. The DNA backbone on both strands must be cut to make a double-strand break

What is the name of the DNA sequence where replication begins? A. replication origin B. initiator C. replication fork D. DNA template

What is the name of the complex that degrades proteins that have reached the end of their lifespan, are damaged, or are misfolded? A. proteasome B. nuclease C. ribosome D. nuclear pore complex

What is the name of the protein that binds the two separated DNA strands to keep them from base pairing again before they can be replicated? A. single-strand binding protein B. helicase C. primase D. sliding clamp

What is the name of the type of damage caused by an improperly paired base in the DNA? A. mismatch B. double-strand break C. depurination D. thymine dimer

What performs the function of bacterial sigma factor in eukaryotes? A. general transcription factors B. initiation proteins C. nucleosomes D. promoters

What recognizes the stop codons in an mRNA? A. release factor B. a specialized tRNA linked to methionine C. nothing D. the 3′ poly-A tail

What types of bonds are formed between histone proteins and DNA to form nucleosome core particles? A. electrostatic interactions B. polar covalent bonds C. nonpolar covalent bonds D. phosphodiester bonds

Which characteristic of a replicating RNA polymerase allows multiple transcripts to be made simultaneously from the same region of DNA? A. The RNA transcript dissociates from the DNA template immediately once complete. B. RNA polymerase is very small. C. RNA remains bound to the gene and helps template more transcripts. D. RNA polymerases can jump over slower RNA polymerases to make more transcript.

Which double-strand break repair mechanism is a simple ligation mechanism? A. nonhomologous end joining B. homologous recombination C. DNA mismatch repair D. DNA ligase

Which nucleic acid often base pairs with itself to fold into complex three-dimensional shapes in the cell? A. RNA B. DNA C. both RNA and DNA D. neither RNA nor DNA

Which of the following DNA sequences is the LEAST likely to accommodate mutations? A. ribosomal RNA sequence B. regulatory DNA sequences C. the coding sequence of a duplicated gene D. DNA sequences found between genes

Which of the following is found only in eukaryotic genomes, and NOT in prokaryotic genomes? A. telomeres B. deoxyribose sugar C. packaging proteins D. chromosomes

Which of the following properties could help RNA be both an information storage unit and a self-replicating molecule? A. RNA can act as a template for making copies of itself. B. RNA is a short-lived molecule. C. RNA cannot catalyze reactions. D. RNA must be made from DNA.

Which of the following specialized DNA sequences provides an attachment point for the segregation of duplicated chromosomes? A. centromeres B. telomeres C. replication origins D. nucleosomes

Which retrotransposon makes up 15% of our genome and encodes its own reverse transcriptase enzyme for transposition? A. L1 element B. Alu sequence C. latent HIV D. bacterial transposons

Why is RNA thought to predate DNA in evolution? A. The sugar in RNA is easier to make with the organic molecules that were present on primitive Earth. B. RNA forms many different types of functional molecules, like snRNA, rRNA and tRNA. C. RNA is less stable than DNA. D. rRNA genes are more conserved through evolution.

_______ is a sequence of DNA that contains the information required for making a particular functional RNA or protein

A gene

___________ is a sequence of DNA that contains the information required for making a particular functional RNA or protein.

A gene

40. Methylation and acetylation are common changes made to histone H3, and the specific combination of these changes is sometimes referred to as the "histone code." Which of the following patterns will probably lead to gene silencing? A lysine 9 methylation B lysine 4 methylation and lysine 9 acetylation C lysine 14 acetylation D lysine 9 acetylation and lysine 14 acetylation

A lysine 9 methylation

In the following condensation reaction, how does ATP power the formation of product A-B?

A phosphate is first transferred to reactant A−OH to form a high energy intermediate.

31. The DNA from two different species can often be distinguished by a difference in the A ratio of A + T to G + C. B ratio of A + G to C + T. C ratio of sugar to phosphate. D presence of bases other than A, G, C, and T. E number of strands in the helix.

A ratio of A + T to G + C.

At what site do all charged tRNAs (with the exception of the initiator tRNA) first bind on the ribosome?

A site

Glycolysis alone captures approximately what percentage of the free energy available in a molecule of glucose? A) 10% B) 20% C) 50% D) 99%

A) 10%

The number of ATP molecules that could be synthesized from the energy released by the transfer of two electrons from NADH to molecular oxygen is A) 2.5. B) 4. C) 3 D) 1.5

A) 2.5.

The pH of the mitochondrial matrix is ___________, which is ___________ than that of the intermembrane space. A) 7.9; higher B) 7.2; lower C) 7.2; higher D) 7.9; lower

A) 7.9; higher

Stage two of photosynthesis (or the light-independent reactions) uses which input molecules to produce organic food molecules? A) ATP, NADPH, CO2 B) O2, NADH, ADP C) H2O, light, chlorophyll D) amino acids, sugars, fatty acids

A) ATP, NADPH, CO2

24) Which of the following can serve as an energy source and as structural support in plant cells? A) Carbohydrates B) Nucleic acids C) Proteins D) Lipids

A) Carbohydrates

25) Which of the following categories includes monosaccharide monomers? A) Carbohydrates B) Proteins C) Nucleic acids D) Lipids

A) Carbohydrates

The rules of which fundamental process were elucidated in the bacterium Escherichia coli (E. coli)? A) DNA Replication B) cell division cycle C) mitosis D) embryonic development

A) DNA Replication

64) Your friend is trying to learn about how to kill bacteria. She reads that preservatives such as citric 64) acid are added to foods because the acidic environment kills bacteria by denaturing their proteins. She thinks this sounds like a lot of scientific jargon and asks you what it means. How can you explain it in simpler terms? A) Denaturing means that the proteins of the bacteria lose their structure and can't function, so the bacteria die. B) Denaturing refers to the fact that the bacterial cells divide too quickly and die. C) The acid causes the cells to swell and burst open, also known as denaturation. D) Denaturing their proteins means that the proteins in bacteria are converted into carbohydrates

A) Denaturing means that the proteins of the bacteria lose their structure and can't function, so the bacteria die.

Why do cells use enzymes to harvest energy from food molecules rather than by direct oxidation? A) Enzymes transfer energy from food to carrier molecules in small steps. B) Enzymes release all the energy from food molecules in a single efficient step. C) Direct oxidation cannot release all the energy from food molecules D) Direct oxidation is energetically unfavorable.

A) Enzymes transfer energy from food to carrier molecules in small steps.

31) When 1 gram of each of these food sources is consumed, which yields the greatest amount of energy in calories? A) Fat B) Phenylalanine C) Sucrose D) Glucose E) Polypeptide

A) Fat

18) Free radicals contain unpaired electrons in their outermost energy shell, so they react readily with 18) other atoms or molecules to reach a more stable state. Which of the following could potentially be a free radical? A) Fluorine (atomic number 9) B) Magnesium (atomic number 12) C) Helium (atomic number 2) D) Neon (atomic number 10)

A) Fluorine (atomic number 9)

53) What maintains the secondary structure of a protein? A) Hydrogen bonds B) Disulfide bonds C) Peptide bonds D) Ionic bonds

A) Hydrogen bonds

29) What type of bond is easily disrupted in aqueous solutions (one in which the solvent is water)? 29) A) Ionic B) Covalent C) Polar covalent

A) Ionic

72) Which of these is NOT a nucleic acid or nucleotide? A) LDL B) RNA C) DNA D) ATP

A) LDL

Which of the following has a higher concentration in the cell to allow it to be available to accept electrons from oxidation of food molecules? A) NAD+ B) NADH C) NADPH D) NADP+

A) NAD+

If cells were undergoing glycolysis but could not carry out fermentation, what products would build up in the cytosol? A) NADH and pyruvate B) ADP and CO2 C) H2O and citric acid D) NAD+ and ATP

A) NADH and pyruvate

Which of the following has the lowest electron affinity? A) NADH dehydrogenase complex B) cytochrome c reductase complex C) cytochrome c oxidase complex D) oxygen

A) NADH dehydrogenase complex

37) The fat substitute Olestra contains a sucrose backbone with six to eight fatty acids attached. How is this different from a naturally occurring fat? A) Naturally occurring fats contain a glycerol and three fatty acids. B) It isn't Olestra and natural fats have the same structure, just different tastes. C) Naturally occurring fats contain a glycerol, two fatty acids, and a phosphate group. D) Naturally occurring fats contain a sucrose backbone and three fatty acid chains.

A) Naturally occurring fats contain a glycerol and three

42) Which of the following is LEAST affected by the presence of water? A) Nonpolar covalent bond B) Polar covalent bond C) Ionic bond D) Hydrogen bond E) Electron-proton interaction

A) Nonpolar covalent bond

75) Which of these biological molecules contain genetic information? A) Nucleic acids B) Carbohydrates C) Lipids D) Proteins

A) Nucleic acids

58) Which of the following refers to the amino acid sequence of proteins? A) Primary B) Secondary C) Tertiary D) Quaternary

A) Primary

61) Which of the following biological molecules are composed of amino acid subunits? A) Proteins B) Lipids C) Carbohydrates D) Nucleic acids

A) Proteins

62) Which of the following may possess primary, secondary, tertiary, and quaternary structures? A) Proteins B) Carbohydrates C) Nucleic acids D) Lipids

A) Proteins

Which of the following microscopy techniques would allow the most detailed image showing the 3D structure of flagellum? A) scanning electron microscopy B) transmission electron microscopy C) high-resolution fluorescence microscopy D) conventional light microscopy

A) Scanning electron microscopy

21) Which of the following provides long-term energy storage for plants? A) Starch B) ATP C) Glycogen D) Glucose E) Cellulose

A) Starch

43) What happens when hydrochloric acid (HCl) dissociates in pure water? A) The HCl molecules separate into H+ and Cl- ions. B) The pH of the solution increases. C) The HCl molecules float on top of the water. D) The water has a decrease of H+ ions. E) The concentration of OH- ions increases.

A) The HCl molecules separate into H+ and Cl- ions.

For a reaction Y à X with a very high equilibrium constant, K, which of the following is true? You can refer to the following two equations in formulating your answer. A) The amount of product will be higher than the amount of substrate at equilibrium. B) The forward reaction rate greatly exceeds the reverse reaction rate at equilibrium. C) The standard free-energy change is large and positive. D) The amount of product and substrate are equal at equilibrium.

A) The amount of product will be higher than the amount of substrate at equilibrium.

In a sperm cell, where are the mitochondria located? A) The mitochondria form elongated tubes that wrap around the flagellar core. B) They are located in a tubular network that are just inside the plasma membrane. C) Mitochondria are randomly scattered around in the cytoplasm of the cell. D) The mitochondria surround the nucleus of the cell.

A) The mitochondria form elongated tubes that wrap around the flagellar core.

Why is the oxidation of NADPH energetically favorable? A) The oxidized form of NADPH is more stable than the reduced form. B) NADPH is the form of the molecule that can gain two high-energy electrons. C) The biosynthetic reactions that are coupled to NADPH oxidation are energetically favorable. D) Oxidation of NADPH breaks a high-energy phosphoanhydride bond.

A) The oxidized form of NADPH is more stable than the reduced form.

Shown below is the mechanism believed to be used for pumping protons by cytochrome c oxidase across the inner mitochondrial membrane. One of the steps shown is unidirectional because it is driven by the energy of electron transport. Why must this step be performed only in one direction? A) The protons could be also captured from the intermembrane space and released back into the matrix. B) The complex would stay stuck in the closed (center conformation). C) The inner membrane would become porous to all molecules. D) The H+ affinity in the two conformations would reverse.

A) The protons could be also captured from the intermembrane space and released back into the matrix.

33) A single covalent chemical bond represents the sharing of how many electrons? 33) A) Two B) Three C) One D) Four E) Six

A) Two

A base is a molecule that will ___________ a proton in water. A) accept B) donate C) repel D) neutralize

A) accept

Fatty acids can be used to produce energy by conversion to ___________ in the ___________ of the cell. A) acetyl CoA; mitochondria B) pyruvate; endoplasmic reticulum C) lipids; plasma membrane D) NADH; cytosol

A) acetyl CoA; mitochondria

35) New government regulations require that foods containing trans fats be labeled appropriately. A trans fat is formed when food manufacturers turn liquid oils into solid fats by adding hydrogen to vegetable oils. This hydrogenation process produces a solid fat because adding the hydrogen A) allows the fatty acid chains to pack together more tightly. B) causes a phospholipid to form. C) forms a wax molecule. D) allows fats to form tertiary and quaternary structures.

A) allows the fatty acid chains to pack together more tightly.

How does binding of GTP to a GTP-binding protein affect its activity? A) always activates the protein B) always inactivates the protein C) does not affect the protein D) could activate or inactivate the protein

A) always activates the protein

Reactions that build larger molecules in the cell are called ___________; reactions that break down molecules into smaller ones are called ___________. A) anabolic; catabolic B) catabolic; anabolic C) anabolic; metabolic D) metabolic; anabolic

A) anabolic; catabolic

A molecule with a lot of polar covalent bonds is likely to A) be highly soluble in water. B) be hydrophobic. C) form ionic bonds. D) contain only atoms with low electronegativity.

A) be highly soluble in water.

Why is CO2 an end product of cellular respiration? A) because it is the most stable form of carbon in our atmosphere B) because it can accept electrons and produce a reduced form of carbon C) because it captures light energy for photosynthesis D) because plants can use it for respiration

A) because it is the most stable form of carbon in our atmosphere

38) Two categories of organic compounds typically provide energy for living systems. Representatives of these two classes are A) carbohydrates and proteins. B) carbohydrates and lipids. C) proteins and nucleic acids. D) lipids and proteins. E) carbohydrates and nucleic acids.

A) carbohydrates and proteins.

All amino acids have which of the following chemical groups in common? A) carboxyl group B) aromatic ring group C) methyl group D) hydrocarbon tail

A) carboxyl group

54) Water moves through a plant because of the property of A) cohesion. B) high heat of vaporization. C) high specific heat. D) high heat of fusion.

A) cohesion.

Long polymers are made from single subunits in cells using a ___________ reaction, which ___________ water. A) condensation; releases B) hydrolysis; uses C) condensation; uses D) hydrolysis; releases

A) condensation; releases

Disulfide bonds stabilize protein shape outside the cell by A) covalent bonds between cysteines. B) noncovalent bonds between charged side chains. C) hydrophobic interactions within the lipid bilayer. D) hydrogen bonds with water molecules.

A) covalent bonds between cysteines.

15) The carbohydrate in DNA is A) deoxyribose. B) phosphate. C) glucose. D) ribose. E) cellulose.

A) deoxyribose.

A stretch of amino acids in a polypeptide chain that is capable of independently folding into a defined structure is called a A) domain B) backbone C) subunit D) ligand

A) domain

What is the role of oxygen in the electron transport chain? A) electron acceptor B) coenzyme C) reducing agent D) transporter

A) electron acceptor

1) A substance with specific properties that cannot be broken down or converted into another substance is called a(n) A) element. B) mixture. C) molecule. D) compound. E) ion.

A) element.

The first living things on Earth probably generated ATP by what mechanism? A) fermentation B) oxidative phosphorylation C) photosynthesis D) carbon fixation

A) fermentation

Which of the following is a role that sugars can play outside of their role in energy production and storage? A) formation of support structures B) component of transport vesicle membrane C) enzymatic catalysis D) primary component of cell membrane

A) formation of support structures

46) A neutral solution A) has equal amounts of H+ and OH-. B) has no H+. C) has a pH of 0. D) has no OH-. E) is hydrophobic.

A) has equal amounts of H+ and OH-.

45) If a substance measures 7 on the pH scale, that substance A) has equal concentrations of H+ and OH- ions. B) is basic. C) probably lacks OH- ions. D) has a higher concentration of OH- than H+ ions. E) may be lemon juice.

A) has equal concentrations of H+ and OH- ions.

Individuals with inherited diseases causing mitochondrial dysfunction typically experience which of the following symptoms? A) heart problems B) sterilit C) bone deformities D) light sensitivity

A) heart problems

Living systems can generate and maintain order without violating the second law of thermodynamics because they generate A) heat B) order C) decreased entropy D) macromolecules

A) heat

If a gene sequence in one organism is highly similar to the sequence of another gene in another organism it is called A) homologous B) related. C) protein-coding. D) comparative.

A) homologous

10) If digestion is ________, then synthesis is ________. A) hydrolysis;dehydration synthesis B) inorganic;organic C) dehydration synthesis; hydrolysis D) organic; inorganic

A) hydrolysis;dehydration synthesis

If a reaction is energetically favorable (exergonic), then it must produce a(n) A) increase in entropy. B) decrease in heat. C) increase in activation energy. D) decrease in reaction time.

A) increase in entropy.

15) Atoms or molecules that have gained or lost electrons are called A) ions. B) covalent. C) acids. D) bases. E) buffers.

A) ion

49) Milk of magnesia is often used to treat stomach upset. It has a pH of 10. Based on this information, milk of magnesia A) is a base. B) is hydrophobic. C) has the same pH as stomach acid. D) is an acid.

A) is a base.

26) The atomic number of hydrogen is 1. Based on this fact, all of the following must be true of hydrogen gas (H2) EXCEPT that it A) is a polar molecule. B) shares one pair of electrons between the two hydrogen atoms. C) uses covalent bonds to form the molecule. D) is a stable molecule.

A) is a polar molecule.

The defining property that differentiates prokaryotic cells from eukaryotic cells is their A) lack of a nucleus B) presence of a flagellum C) small size D) cell division

A) lack of a nucleus

The cytochrome complexes contain heme prosthetic groups, which have a higher redox potential than the iron-sulfur centers found in other electron-transport chain complexes like NADH dehydrogenase. Where in the electron-transport chain would the cytochrome complexes thus be located relative to iron-sulfur center complexes? A) later in the chain B) earlier in the chain C) It cannot be determined. D) at the same point of the chain

A) later in the chain

Covalent bonds in macromolecules are primarily important for A) linking together monomers. B) forming the three-dimensional folded conformation. C) interactions with other macromolecules. D) enzyme-substrate binding.

A) linking together monomers.

A binding site on the surface of a protein interacts specifically with another protein through A) many weak noncovalent interactions. B) a few strong noncovalent interactions. C) many weak covalent interactions. D) a few strong covalent interactions.

A) many weak noncovalent interactions.

Compared to eukaryotes, prokaryotic organisms are A) more abundant and more widespread B) less abundant and less widespread C) more abundant and less widespread D) less abundant and more widespread

A) more abundant and more widespread

59) If you place a paper towel in a dish of water, the water will A) move up the towel as the water adheres to the paper towel while the cohesive water molecules stay bound to each other. B) dissolve the towel because water is a good solvent. C) separate into H+ and OH- ions, which will react with the paper towel molecules. D) move away from the towel because water molecules have hydrophobic interactions. E) move up the towel because water molecules move quickly as it vaporizes.

A) move up the towel as the water adheres to the paper towel while the cohesive water molecules stay bound to each other.

3) The atomic number of an atom is defined as the A) number of protons in the atomic nucleus. B) number of neutrons in the atomic nucleus. C) total number of electrons and neutrons. D) number of electrons in the outermost energy level. E) total number of energy shells.

A) number of protons in the atomic nucleus.

Lysosomes and Peroxisomes both perform a series of reactions to break down molecules, but one difference between them is that A) peroxisomes contain hydrogen peroxide B) lysosomes break down toxic molecules C) peroxisomes digest molecules for reuse D) lysosomes are large and form an interconnected network

A) peroxisomes contain hydrogen peroxide

12) Keratin and silk are examples of ________, whereas glucose and maltose are examples of ________. A) proteins; carbohydrates B) carbohydrates; proteins C) nucleic acids; lipids D) proteins; lipids

A) proteins; carbohydrates

How is pyruvate imported into the mitochondrial matrix for use in the citric acid cycle? A) proton gradient-driven symport B) sodium gradient-driven antiport C) ATP-driven pyruvate pump D) diffusion through porin complexes in the membrane

A) proton gradient-driven symport

In an enzymatic reaction, a molecule gains an electron. This is known as a(n) ___________ reaction. A) reduction B) oxidation C) hydrogenation D) electronegative

A) reduction

Two atoms held together solely by ionic bonds are referred to as a(n) A) salt. B) molecule. C) element. D) isotope.

A) salt.

All living cells A) share the same basic chemistry B) have the same overall shape C) are nearly the same size D) need to replicate within another cell

A) share the same basic chemistry

If cells that cannot carry out fermentation were grown in anaerobic conditions, at which step would glycolysis halt? A) step 6: where NAD+ is converted to NADH B) step 1: using ATP to phosphorylate glucose C) step 10: production of pyruvate D) step 4: the cleavage of the 6-carbon molecule into two 3-carbon molecules

A) step 6: where NAD+ is converted to NADH

62) If you place a feather on the surface of a bowl of water, the feather remains suspended on the surface due to the A) surface tension of the water. B) polarity of the water. C) density of the water. D) fact that water is a good solvent.

A) surface tension of the water.

Which of the following is an inorganic compound? A) table salt (e.g., NaCl) B) simple sugars (e.g., glucose) C) amino acids (e.g., phenylalanine) D) saturated fatty acids (e.g., palmitic acid)

A) table salt (e.g., NaCl)

The low redox potential of NADH means that it has a A) tendency to give up electrons. B) low free energy. C) high electron affinity. D) very stable bond.

A) tendency to give up electrons.

What is gluconeogenesis? A) the synthesis of glucose from pyruvate B) the mobilization of glucose from glycogen stores C) the production of glucose from starch D) the blockage of glycolysis at the first step

A) the synthesis of glucose from pyruvate

The cell components that move materials from one organelle to another are called A) transport vesicles B) endoplasmic reticulum C) Golgi apparatus D) cytosol

A) transport vesicles

The function of feedback inhibition of an enzymatic pathway is to A) turn off synthesis of a product when it is in abundance. B) accumulate large amounts of important biological molecules. C) irreversibly shut down a biosynthetic pathway. D) increase concentrations of intermediates to drive the reaction forward.

A) turn off synthesis of a product when it is in abundance.

What is the value of ΔG at equilibrium? A) zero B) positive C) negative D) It depends on the concentration of substrates and products.

A) zero

76) Different types of living matter often have different forms of the same elements in their bodies. For 89) example, the nitrogen in an animal often has a slightly different atomic structure than the nitrogen in a plant. Recently, nutritionists have discovered how to deduce the diets of various animal species by examining the type of nitrogen (and other elements) inside their bodies. What is the chemical basis behind this scenario? A) Isotopes of the same element have the same atomic number but different atomic masses. B) Radioactive elements can be used to trace the paths of molecules through the body. C) Antioxidants buffer the potential damage that free radicals do to cells. D) Hydrophobic interactions keep water molecules from forming bonds with fats and oils. E) Covalent bonds result when two atoms share electrons.

A)Isotopes of the same element have the same atomic number but different atomic masses.

A. If 0.5 mole of glucose weighs 90 g, what is the molecular mass of glucose? B. What is the concentration, in grams per liter (g/L), of a 0.25 M solution of glucose? C. How many molecules are there in 1 mole of glucose?

A. 180 daltons. A mole of a substance has a mass equivalent to its molecular weight expressed in grams. B. 45 g/L C. 6 × 1023 molecules

A. How many carbon atoms does the molecule represented in Figure Q2-50 have? B. How many hydrogen atoms does it have? C. What type of molecule is it? Figure Q2-50

A. 20 carbon atoms B. 31 hydrogen atoms C. A fatty acid (Figure A2-50 is arachidonic acid, an essential fatty acid required by most mammals)

33. The human genome comprises 23 pairs of chromosomes found in nearly every cell in the body. Answer the quantitative questions below by choosing one of the numbers in the following list: 1. 23 2. 69 3. >1000 4. 46 5. 92 6. >109 A. How many centromeres are in each cell? What is the main function of the centromere? B. How many telomeres are in each cell? What is their main function? C. How many replication origins are in each cell? What is their main function?

A. 46 centromeres. The centromeres have a key role in the distribution of chromosomes to daughter cells during mitosis by binding to spindle microtubules. B. 92 telomeres (two on each chromosome). Telomeres serve to protect the ends of chromosomes and to enable complete replication of the DNA of each chromosome all the way to its tips. C. There are far more than 200 replication origins in a human cell, probably about 10,000. These DNA sequences direct the initiation of DNA synthesis needed to replicate chromosomes.

25. Which of the following is NOT true? A. A cell can temporarily decondense its chromatin to silence genes during differentiation. B. A cell can temporarily decondense its chromatin to give proteins rapid, localized access to specific DNA sequences. C. A cell can temporarily decondense its chromatin to allow access to specific DNA sequences for replication, repair, or gene expression.

A. A cell can temporarily decondense its chromatin to silence genes during differentiation.

Eukaryotic cells have their DNA molecules inside their nuclei. However, to package all the DNA into such a small volume requires the cell to use specialized proteins called histones. Histones have amino acid sequences enriched for lysines and arginines. A. What problem might a cell face in trying to package DNA into a small volume without histones, and how do these special packaging proteins alleviate the problem? B. Lysine side chains are substrates for enzymes called acetylases. A diagram of an acetylated lysine side chain is shown in Figure Q2-72. How do you think the acetylation of lysines in histone proteins will affect the ability of a histone to perform its role (refer to your answer in part A)? Figure Q2-72

A. DNA is a nucleic acid polymer in which each monomer has a negatively charged phosphate group. The negative charges will naturally repel each other, so in order to wrap the high density of negative charges into a small space, positively charged molecules must be present. Histones accomplish this because they are rich in lysines and arginines, which are positively charged in solution at pH 7. B. A histone with acetylated lysine residues will not be as good at packaging the DNA. The addition of the acetyl group to the terminal amino on the lysine side chain lowers the histone's net positive charge, which makes it less effective at buffering the negative charges on the DNA backbone.

Indicate whether the statements below are true or false. If a statement is false, explain why it is false. A. A disaccharide consists of a sugar covalently linked to another molecule such as an amino acid or a nucleotide. B. The hydroxyl groups on monosaccharides are reaction hot spots and can be replaced by other functional groups to produce derivatives of the original sugar. C. The presence of double bonds in the hydrocarbon tail of a fatty acid does not greatly influence its structure.

A. False. A disaccharide consists of two sugar molecules that undergo a condensation reaction to form a covalent bond (known as a glycosidic linkage). B. True. C. False. The presence of a double bond in the hydrocarbon chain of a fatty acid causes a kink in the chain, decreasing its flexibility and packing with neighboring hydrocarbon chains

Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. When a mouse cell is fused with a human cell, the movement of the respective membrane proteins is restricted to their original locations at the time of fusion. B. Epithelial cell membranes are asymmetric, and proteins from the apical side of the cell membrane cannot diffuse into the basal side of the membrane. C. The longest carbohydrates found on the surfaces of cells are linked to lipid molecules. D. The only role of the carbohydrate layer on the cell surface is to absorb water, which creates a slimy surface and prevents cells from sticking to each other.

A. False. After about 1 hour, the mouse and human proteins present on the surface of the fused cell are found evenly dispersed throughout the plasma membrane. B. True. C. False. The very long, branched polysaccharides that are attached to integral membrane proteins are much longer than the oligosaccharides covalently attached to membrane lipids. D. False. Although the absorption of water is an important role of the carbohydrates on the surface of the plasma membrane, a second critical role is that of cell-cell recognition, which is important in immune responses, wound healing, and other processes that rely on cell-type-specific interactions.

Indicate whether the statements below are true or false. If a statement is false, explain why it is false. A. The chemistry of life is carried out and coordinated primarily by the action of small molecules. B. Carbon-based compounds make up the vast majority of molecules found in cells. C. The chemical reactions in living systems are loosely regulated, allowing for a wide range of products and more rapid evolution.

A. False. Although small molecules are important in many processes, the chemical reactions in living systems are regulated by the coordinated action of large polymeric molecules. B. True. C. False. The chemical reactions in living systems are very tightly controlled, ensuring that events occur at the proper time and at the proper location inside the cell.

Indicate whether the statements below are true or false. If a statement is false, explain why it is false. A. Any covalently bonded H atom can participate in a hydrogen bond if it comes in close proximity with an oxygen atom that forms part of a water molecule. B. Protons are constantly moving between water molecules, which means there is an overall equilibrium between hydroxyl ions and hydronium ions in aqueous solutions. C. A strong base is defined as a molecule that can readily remove protons from water.

A. False. Hydrogen atoms that are covalently bonded to carbon atoms do not participate in hydrogen bonds because these hydrogens have almost no net positive charge. B. True. C. True.

Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. Lipid-linked proteins are classified as peripheral membrane proteins because the polypeptide chain does not pass through the bilayer. B. A protein can be embedded on the cytosolic side of the membrane bilayer by employing a hydrophobic α helix. C. A protein that relies on protein-protein interactions to stabilize its membrane association is classified as a peripheral membrane protein because it can be dissociated without the use of detergents. D. Membrane proteins that pump ions in and out of the cell are classified as enzymes.

A. False. Lipid-linked proteins are classified as integral membrane proteins because although they are not transmembrane proteins, they are covalently bound to membrane lipids and cannot be dissociated without disrupting the membrane's integrity. B. False. An embedded protein employs an amphipathic helix. The hydrophobic side interacts with the fatty acid tails of the membrane lipids, and the hydrophilic portion interacts with the aqueous components of the cytosol. C. True. D. False. Membrane proteins that pump ions in either direction across the membrane are in the functional class of transporters.

Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. In order to study the activity of isolated transmembrane proteins, the membrane lipids must be completely stripped away. B. FRAP is a method used to study the movement of individual proteins. C. SDS is a mild detergent that is useful for the reconstitution of membrane components. D. The speed of fluorescent signal recovery during a FRAP assay is a measure of lateral mobility for the molecule of interest.

A. False. The region of the protein that normally crosses the membrane must be stabilized by the presence of phospholipids for the purified protein to be active. For this reason, purified membrane proteins are often reconstituted into artificial lipid bilayers. B. False. The FRAP method involves photobleaching of a small region of the membrane, which contains hundreds of target molecules, and follows the displacement of these molecules with neighboring molecules that have not been bleached. C. False. SDS is a strong, ionic detergent that will break up membrane bilayers and also denature proteins. D. True.

Indicate whether the statements below are true or false. If a statement is false, explain why it is false. A. "Nonpolar interactions" is simply another way of saying "van der Waals attractions." B. Condensation reactions occur in the synthesis of all the macromolecules found in cells. C. All proteins and RNAs pass through many unstable conformations as they are folded, finally settling on one single, preferred conformation.

A. False. Van der Waals attractions describe the general attractive forces between all atoms. The contact distance between any two nonbonded atoms is the sum of the van der Waals radii. Nonpolar interactions are based on the exclusion of hydrophobic molecules from a hydrophilic environment. B. True. C. True.

23. What is the most highly condensed form of chromatin? A. Heterochromatin B. 30-nm chromatin fibers C. Euchromatin

A. Heterochromatin

19. What histone protein (considered a "linker" histone) is thought to pull nucleosomes together into a regular repeating array, resulting in a 30-nm fiber? A. Histone H1 B. Histone H2A C. Histone H2B D. Histone H3 E. Histone H4

A. Histone H1

18. Which statement is true about the tight association of histone proteins and DNA? A. Histone proteins have a high proportion of positively charged amino acids, which attract the negatively charged phosphate groups on DNA. B. Histone proteins have deep grooves into which a DNA double helix tightly fits.

A. Histone proteins have a high proportion of positively charged amino acids, which attract the negatively charged phosphate groups on DNA.

3. The polarity in a DNA strand is indicated by referring to one end as the 3′ end and the other as the 5′ end. Which structure is on the 3′ end? A. Hydroxyl group B. Phosphate group C. Nitrogenous base

A. Hydroxyl group

Data for the mobility of three different proteins (X, Y, and Z) using fluorescence recovery after photobleaching (FRAP) are shown in Figure Q11-60A. Separately, single-particle tracking (SPT) data were collected for these samples, as shown in Figure Q11-60B A. Assign an SPT profile (A, B, or C) to each of these proteins on the basis of the respective FRAP profiles. B. It is important to remember that in each of these experiments, the results reflect a real, physical difference in the way in which these proteins are situated in the plasma membrane. Provide a plausible explanation for the differences observed in proteins X, Y, and Z.

A. Protein X should have an SPT profile as shown in (B); FRAP data for protein Y correlates with SPT data shown in (A); and Z seems to have intermediate mobility, as shown in the SPT profile (C). B. Protein X is highly mobile, so it is probably a small protein that is not anchored to anything and is not part of a larger, multiprotein complex. Protein Y is relatively immobile, indicating that it is probably anchored to the cell cortex. Protein Z is mobile, but less so than protein X. If protein Z bound to other proteins as part of a complex, the higher molecular weight would retard its observed movement in the membrane.

Consider the following image of multiple genes (a and b) on a chromosome and then answer the question. Based on the figure, which of these statements is/are correct?

A. RNA is always polymerized in the 5'-to-3' direction. B. For different genes, opposite strands of DNA can serve as a template.

Sodium dodecyl sulfate (SDS) and Triton X-100 are both detergents that can be used to lyse cells. A. If the goal is to study the activity of membrane proteins after cell lysis, explain why SDS would not be a good choice. B. How does Triton X-100 work in cell lysis, and why is it a better choice of detergent to help you extract proteins?

A. SDS is a strong ionic detergent. When cells are exposed to SDS, membrane proteins are not only extracted from the membrane, they are completely unfolded. After denaturation, they cannot be studied as functional molecules. B. Triton X-100 has a smaller nonpolar portion and a polar but uncharged end, allowing it to mimic more closely the type of solvation effect of the membrane lipids. Triton X-100 forms a shell around the hydrophobic portion of the protein without disrupting the existing structure. This makes it possible to then place the protein into a new, synthetic membrane bilayer for study.

A. Sketch three different ways in which three water molecules could be held together by hydrogen-bonding. B. On a sketch of a single water molecule, indicate the distribution of positive and negative charge (using the symbols δ+ and δ-). C. How many hydrogen bonds can a hydrogen atom in a water molecule form? How many hydrogen bonds can the oxygen atom in a water molecule form?

A. See Figure A2-37A. B. See Figure A2-37B. C. Hydrogen can form one; oxygen two.

Glycolipids are found on the surface of healthy cells, and contribute to the cell's defense against chemical damage and infectious agents. A. In which organelle are sugar groups added to membrane lipids? B. By what mechanism are glycolipids transported to the plasma membrane and presented to the extracellular environment? Draw a diagram to support your answer to part B.

A. The Golgi apparatus. B. Membranes that contain newly synthesized glycolipids bud from the Golgi apparatus to form vesicles. These vesicles then fuse with the plasma membrane. The glycolipids that were facing the lumen of the Golgi will now face the extracellular environment (Figure A11-26).

4. What does the term 'genetic code' refer to? A. The correspondence between the 4-letter nucleotide alphabet of DNA and the 20-letter amino acid alphabet of proteins B. The set of genes encoded in an organism's DNA C. The substitution of uracil (U) for thymine (T) in an RNA molecule D. The linear sequence of nucleotides in a gene

A. The correspondence between the 4-letter nucleotide alphabet of DNA and the 20-letter amino acid alphabet of proteins

Your lab director requests that you add new growth medium to the mammalian cell cultures before heading home from the lab on a Friday night. Unfortunately, you need to make fresh medium because all the premixed bottles of medium have been used. One of the ingredients you know you need to add is a mix of the essential amino acids (those that cannot be made by the cells, but are needed in proteins). On the shelf of dry chemicals you find the amino acids you need, and you mix them into your medium, along with all the other necessary nutrients, and replace the old medium with your new medium. On Sunday, you come in to the lab just to check on your cells and find that the cells have not grown. You are sure you made the medium correctly, but on checking you see that somebody wrote a note on the dry mixture of amino acids you used: "Note: this mixture contains only ᴅ-amino acids." A. What is the meaning of the note and how does it explain the lack of cell growth in your culture? B. Are there any organisms that could grow using this mixture? Justify your answer.

A. The note indicates that the mixture contains only one of the two possible stereoisomers (ʟ or ᴅ). Because mammalian cells use only the ʟ stereoisomer, the ᴅ-amino acid mixture could not be used and therefore it is as though no amino acids were added at all. B. Not unless ʟ-amino acids were also mixed in. Certain types of bacteria use ᴅ-amino acids to produce their cell walls, but they would still require ʟ-amino acids for the rest of the proteins they make.

20. How do chromatin-remodeling complexes work? A. They use the energy from ATP hydrolysis to alter nucleosomes and make certain regions of the DNA more accessible to other proteins. B. They bind to nucleosomes in the 30-nm fiber and induce another level of packing, obscuring DNA from binding by other proteins. C. They add methyl groups to the tails of histones in order to attract other proteins.

A. They use the energy from ATP hydrolysis to alter nucleosomes and make certain regions of the DNA more accessible to other proteins.

24. Histone tail modifications establish and maintain the different chromatin structures found in heterochromatin and euchromatin. A. True B. False

A. True

Indicate whether the statements below are true or false. If a statement is false, explain why it is false. A. There are four elements that constitute 99% of all the atoms found in the human body. B. Copper, zinc, and manganese are among 11 nonessential trace elements that contribute less than 0.1% of all the atoms in the human body. C. Approximately 0.9% of the atoms in the human body come from seven essential elements—Na, Mg, K, Ca, P, S, and Cl—all of which form stable ions in aqueous solution.

A. True. B. False. Cu, Zn, and Mn are essential trace elements in the human body. C. False. Na, Mg, K, Ca, and Cl form ions in aqueous solution, but P and S form covalent bonds in order to fill their outer electron shells.

Indicate whether the statements below are true or false. If a statement is false, explain why it is false. A. Electron shells fill discrete regions around the nucleus of the atom and limit the number of electrons that can occupy a specific orbit. B. H, C, O, and N are the most common elements in biological molecules because they are the most stable. C. Some atoms are more stable when they lose one or two electrons, even though this means they will have a net positive charge.

A. True. B. False. H, C, N, and O are the most common elements in biological molecules because their outer shells are unfilled, making them highly reactive. C. True.

Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. Although cholesterol is a hydrophobic molecule, it has a hydrophilic head group like all other membrane lipids. B. Phosphatidylserine is the most abundant type of phospholipid found in cell membranes. C. Glycolipids lack the glycerol component found in phospholipids. D. The highly ordered structure of the lipid bilayer makes its generation and maintenance energetically unfavorable.

A. True. B. False. Phosphatidylcholine is the most abundant phospholipid found in cell membranes. C. True. D. False. The formation of a lipid bilayer is energetically favorable.

Indicate whether the statements below are true or false. If a statement is false, explain why it is false. A. Electrons are constantly moving around the nucleus of the atom, but they can move only in discrete regions. B. There is no limit to the number of electrons that can occupy the fourth electron shell. C. Atoms with unfilled outer electron shells are especially stable and are therefore less reactive.

A. True. B. False. The fourth electron shell has the capacity to hold 18 electrons. C. False. Atoms that have their outer electron shells filled are the most stable and least reactive. Atoms with unfilled outer shells are more reactive because they tend to share or transfer electrons to fill and therefore stabilize the outer shell.

The figure below shows a depiction of an antibody. Which label correctly identifies the region(s) of the antibody that contains variable amino acids for binding of a specific antigen?

A. Yellow (FEEDBACK: Unique antigen-binding sites in antibodies are formed by varying the terminal amino acid sequences in the heavy chain and the light chain, which come together into a unique three-dimensional conformation for specific side-chain interactions with the antigen. Since each antibody is made up of two heavy chains and two light chains, there are two antigen-binding sites per antibody.

A protein chain folds into its stable and unique three-dimensional structure, or conformation, by making many noncovalent bonds between different parts of the chain. Such noncovalent bonds are also critical for interactions with other proteins and cellular molecules. From the list provided, choose the class(es) of amino acids that are most important for the interactions detailed below. A. forming ionic bonds with negatively charged DNA B. forming hydrogen bonds to aid solubility in water C. binding to another water-soluble protein D. localizing an "integral membrane" protein that spans a lipid bilayer E. tightly packing the hydrophobic interior core of a globular protein acidic nonpolar basic uncharged polar

A. basic B. uncharged polar C. uncharged polar, basic, and acidic D. nonpolar E. nonpolar

11. The structure that allows each duplicated eukaryotic chromosome to be separated during M phase is a: A. centromere. B. telomere. C. mitotic spindle. D. histone.

A. centromere.

A. In which scientific unit is the strength of a chemical bond usually expressed? B. If 0.5 kilocalories of energy are required to break 6 × 1023 bonds of a particular type, what is the strength of this bond?

A. kilocalories per mole (or kilojoules per mole) B. 0.5 kcal/mole

5. Each chromosome contains: A. one long DNA molecule. B. one long RNA molecule. C. one long sequence of amino acids. D. a single gene for a protein.

A. one long DNA molecule.

A. Write out the sequence of amino acids in the following peptide, using the full names of the amino acids. Pro-Val-Thr-Gly-Lys-Cys-Glu B. Write the same sequence with the single-letter code for amino acids. C. According to the conventional way of writing the sequence of a peptide or a protein, which is the C-terminal amino acid and which is the N-terminal amino acid in the above peptide?

A. proline-valine-threonine-glycine-lysine-cysteine-glutamic acid (or glutamate) B. PVTGKCE C. C-terminal is glutamic acid (or glutamate); N-terminal is proline

In the presence of high levels of ___________, the enzyme phosphofructokinase is inhibited.

ATP

Stage two of photosynthesis (or the light-independent reactions) uses which input molecules to produce organic food molecules?

ATP, NADPH, CO2

hydrolyzes ATP

ATPase

Hydrogen bonding between N-H and C=O groups of every fourth amino acid within a polypeptide chain results in which type of folding pattern?

Alpha-helix (D) (FEEDBACK: The hydrogen bonds that form a β-pleated sheet structure occur between the N-H and C=O groups of amino acids in different segments of a single polypeptide chain lying side by side. Amyloid structures are β sheets that interlock with each other through their side chains. The α helices are formed by hydrogen bonds between every fourth amino acid in the primary structure)

Translation takes place in a series of four steps. Which of these best describes this four-step cycle during elongation?

An aminoacyl-tRNA binds to the vacant A site on the ribosome; a peptide bond forms; the large subunit of the ribosome translocates, moving the bound tRNAs to the E and P sites; the small subunit of the ribosome translocates, ejecting the tRNA from the E site

Anemia, a condition that results in individuals with a low red blood cell count, can be caused by a number of factors. Why do individuals with defects in the spectrin protein often have this condition?

Cell membranes are fluid, and thus proteins can diffuse laterally within the lipid bilayer. However, sometimes the cell needs to localize proteins to a particular membrane domain. Name three mechanisms that a cell can use to restrict a protein to a particular place in the cell membrane.

Any combination of the following four answers is acceptable. 1. The protein can be attached to the cell cortex inside the cell. 2. The protein can be attached to the extracellular matrix outside the cell. 3. The protein can be attached to other proteins on the surface of a different cell. 4. The protein can be restricted by a diffusion barrier, such as that set up by specialized junctional proteins at a tight junction.

You are trying to make a synthetic copy of a particular protein but accidentally join the amino acids together in exactly the reverse order. One of your classmates says the two proteins must be identical, and bets you $20 that your synthetic protein will have exactly the same biological activity as the original. After having read this chapter, you have no hesitation in staking your $20 that it won't. What particular feature of a polypeptide chain makes you sure your $20 is safe and that the project must be done again.

As a peptide bond has a distinct chemical polarity, a polypeptide chain also has a distinct polarity (see Figure A2-68). The reversed protein chain cannot make the same noncovalent interactions during folding and thus will not adopt the same three-dimensional structure as the original protein. The activities of these two proteins will definitely be different, because the activity of a protein depends on its three-dimensional structure. It is unlikely that the reverse chain will fold into any well-defined, and hence functionally useful, structure at all, because it has not passed the stringent selective pressures imposed during evolution.

The amino acid histidine is often found in enzymes. Depending on the pH of its environment, sometimes histidine is neutral and at other times it acquires a proton and becomes positively charged. Consider an enzyme with a histidine side chain that is known to have an important role in the function of the enzyme. It is not clear whether this histidine is required in its protonated or its unprotonated state. To answer this question, you measure enzyme activity over a range of pH, with the results shown in Figure Q2-40. Which form of histidine is necessary for the active enzyme? Figure Q2-40

Assuming that the change in enzyme activity is due to the change in the protonation state of histidine, the enzyme must require histidine in the protonated, charged state. The enzyme is active only at low, acidic pH, where the proton (or hydronium ion) concentration is high; thus, the loss of a proton from histidine will be disfavored so that histidine is likely to be protonated.

You explain to a friend what you have learned about Avogadro's number. Your friend thinks the number is so large that he doubts there is even a mole of living cells on the Earth. You have recently heard that there are about 50 trillion (5 × 1013) human cells in each adult human body and that each human contains more bacterial cells (in the digestive system) than human cells, so you bet your friend $5 that there is more than a mole of cells on Earth. The human population is approximately 7 billion (7 × 109). What calculation can you show your friend to convince him you are right?

Avogadro's number, or 6 × 1023, is the number of atoms (or units) in a mole. If you multiply the number of people on Earth by the number of cells in the human body, then double it to account for the bacteria, you will calculate: (7 × 109) × (1 × 1014) = 7 × 1023. Thus, even when only considering the human population and the associated microbial populations, you can estimate more than a mole of living cells on Earth. You win $5.

Germ-line mutations that are deleterious are likely to A. be preserved in a population. B. be lost from a population. C. be preserved or lost depending on chance. D. expand and be duplicated in a population.

How does Polymerase help maintain the accuracy of DNA replication? A. Polymerase never makes mistakes; bases are added based on strict complementarity. B. DNA polymerase can cut out improperly base-paired nucleotides and add the correct one during synthesis. C. Polymerase fixes its mistakes by adding the right base during the next round of replication. D. After DNA replication is complete, the polymerase re-scans the entire chromosome to check for errors.

In bacteria, how does the cell recognize which strand is the newly synthesized strand and thus contains the mismatch? A. The newly synthesized strand is methylated. B. The newly synthesized strand is unmethylated. C. The sequences on both strands are cut. D. The sequence on the newly synthesized strand is made of RNA.

In eukaryotes, multiple genes can be expressed simultaneously by A. the arrangement of multiple genes into an operon. B. the binding of a specific transcriptional regulator to several genes. C. the binding of a mediator complex to several genes at once. D. a repressor protein binding to multiple operators.

Mutations in which of the following elements would abrogate RNA polymerase's ability to activate gene expression? A. regulatory DNA sequence region B. promoter C. transcription termination site D. major groove

Mutations that occur in germ-line cells are the only ones that lead to evolutionary change because A. germ cells are the only ones that express their DNA. B. germ cells form progeny. C. germ cells undergo meiosis. D. germ cell mutations can lead to cancer.

The information in an mRNA molecule is converted into protein sequence using A. three consecutive bases, with one nucleotide overlapping between triplets. B. three consecutive bases, with no overlap between triplets. C. four consecutive bases, with two nucleotides overlapping between quadruplets. D. four consecutive bases, with no overlap between quadruplets.

The structural feature of DNA that hints at the mechanism for its replication is the A. antiparallel strands. B. complementary base pairing. C. double helix. D. constant diameter.

The technique whereby human chromosomes are stained and identified is called a A. chromosome display. B. karyotype. C. genotype. D. phenotype.

What is a function of the nucleolus? A. to enclose sex chromosomes into a membrane-bound organelle B. to assemble ribosomal RNA and proteins into ribosomes C. to assist in the segregation of chromosomes during mitosis D. to form the nuclear lamina

What is the name of the enzyme that fills the sequence gaps after primers are removed from a newly synthesized DNA strand? A. primase B. repair polymerase C. DNA ligase D. nuclease

What percentage of human genes have clearly recognizable homologs in the fruit fly? A. 10% B. 50% C. 99% D. 74%

When Griffith injected heat-killed infectious bacteria mixed with live harmless bacteria, he found that the mice died because A. the heat-killed infectious bacteria were not actually dead. B.the live harmless bacteria were transformed into infectious bacteria. C. the heat-killed infectious bacteria were able to kill the mice on their own. D. the live harmless bacteria were able to kill the mice on their own

When are chromosomes in their most compacted form? A. during interphase B. during mitosis C. during replication D. They are always equally compacted.

Which of the following is a function of the protein component of chromosomes? a. It carries a portion of the genetic information. b.It packages the DNA strands. c. It contains the enzymes that replicate the DNA. d. It helps to translate the genetic message.

Which of the following is the main point of control for regulating gene expression levels? A. translation B. transcription C. protein degradation D. mRNA degradation

Which of the following is true about "junk DNA"? A. It serves no biological function and is all just a remnant from evolution. B. Portions of junk sequence are conserved between species and thus may be functional. C. It usually codes for proteins but the proteins are nonfunctional in the cell. D. It is found at the ends of chromosomes from over replication during each cell cycle.

Which protein complex mediates the RNAi silencing process by inhibiting RNA polymerase via histone methylation and heterochromatin formation? A. mediator B. RITS C. RISC D. RNase

Which type of transposition mechanism leaves a copy of the transposon in its original position and copies the transposon to a new position? A. cut-and-paste transposition B. replicative transposition C. transposases D. mobilizing transposition

Why does RNA polymerase make more mistakes than DNA polymerase? A. RNA polymerase does not use a template molecule. B. RNA polymerase does not have proofreading activity. C. RNA polymerase uses completely different base-pairing rules. D. RNA polymerase has a faulty mismatch repair system.

___________ is a sequence of DNA that contains the information required for making a particular functional RNA or protein. A. A genome B. A gene C. Genetics D. A chromosome

Glucose has a molecular weight of 180 grams per mole. To prepare 1 liter of a 100 mM solution, how many grams of glucose would you dissolve in water for a total volume of 1 liter? A) 180 B) 18 C) 1.8 D) 1800

B) 18

4) Which of the following best explains the molecular complexity of living organisms? A) Each organism has its own unique set of monomers for use in constructing polymers. B) A small number of monomers can be assembled into large polymers with many different combinations/sequences. C) Although there are not many biological molecules in cells, each one has many different functions. D) Condensation reactions can create different polymers because they can combine virtually any molecules in the cell. E) The large number of different monomers allows for the construction of many polymers.

B) A small number of monomers can be assembled into large polymers with many different

The major products of the citric acid cycle are A) pyruvate and ATP. B) CO2 and NADH. C) H2O and ATP. D) NADH and ATP.

B) CO2 and NADH.

Each molecule of acetyl-CoA entering the citric acid cycle produces two ___________ and four ___________. A) NADH; ATP B) CO2; activated carriers C) ATP; GTP D) activated carriers; H2O

B) CO2; activated carriers

2) Which of the following is NOT an organic molecule? A) Protein B) Carbon monoxide C) Monosaccharide D) Lipid E) Nucleic acid

B) Carbon monoxide

If protein folding is determined by the sequence of amino acids in the polypeptide chain, why are chaperone proteins needed to assist folding in the cell? A) Some proteins cannot fold on their own. B) Certain proteins easily aggregate with other proteins. C) Proteins constantly unfold and refold. D) Protein folding is energetically unfavorable.

B) Certain proteins easily aggregate with other proteins.

50) What do carbohydrates, lipids, and proteins have in common? A) All are inorganic molecules. B) Covalent bonding holds these molecules together. C) All are important enzymes that function within the cell. D) Polymers of these organic molecules form monomers via dehydration synthesis reactions.

B) Covalent bonding holds these molecules together.

23) In humans, dental cavities form when Streptococcus mutans bacteria in the mouth hydrolyze sucrose. Which of the following is (are) the products of this reaction? A) Glucose and galactose B) Glucose and fructose C) Starch D) Glycogen

B) Glucose and fructose

10) For an atom to achieve maximum stability and become chemically inert, what must occur? 10) A) Electron pairs are shared. B) Its outermost energy shell must be completely filled with electrons. C) Ionization occurs. D) The number of electrons must equal the number of protons.

B) Its outermost energy shell must be completely filled with electrons.

56) Which of the following is an example of a protein? A) ATP B) Keratin C) Cellulose D) Estroge

B) Keratin

14) Which molecule is a disaccharide? A) Fructose B) Lactose C) Glucose D) Water

B) Lactose

39) Imagine that you have isolated a mysterious liquid from a sample of food. You add the liquid to a beaker of water and shake vigorously. After a few minutes, the water and the other liquid separate into two layers. To which class of biological molecules does the unknown liquid most likely belong? A) Nucleic acids B) Lipids C) Enzymes D) Carbohydrates E) Proteins

B) Lipids

66) Which of the following is the densest? A) Ice B) Liquid water C) Steam

B) Liquid water

25) What does H-O-H represent? A) Atom of water B) Molecule of water C) Ionic bonding of water D) Mixture including water

B) Molecule of water

28) Which of the following is insoluble in water? A) Sucrose B) Olive oil C) Amino acids D) Salt E) DNA

B) Olive oil

27) Which type of lipid is most important in biological membranes? A) Fat B) Phospholipid C) Oil D) Steroid E) Wax

B) Phospholipid

40) Which of the following results from an unequal sharing of electrons between atoms? A) Nonpolar covalent bond B) Polar covalent bond C) Ionic bond D) Hydrogen bond E) Electron-proton interaction

B) Polar covalent bond

41) Which of the following best explains the attraction of water molecules to each other? 41) A) Nonpolar covalent bond B) Polar covalent bond C) Ionic bond c E) Electron-proton interaction

B) Polar covalent bond

65) Scientists consider prions to be "puzzling" proteins. Which of the following is TRUE about prions? A) Prions are proteins that are denatured more easily than most proteins. B) Prions are proteins that cause nearby proteins to change shape and become infectious. C) Prions are infectious proteins that cannot be denatured by any amount of heat. D) Prions are noninfectious proteins.

B) Prions are proteins that cause nearby proteins to change shape and become infectious.

66) Which of the following correctly matches an organic polymer with its monomers, respectively? A) Lipid; steroids B) Protein;amino acids C) Hydrocarbon; monosaccharides D) DNA; ATP E) Carbohydrate; polysaccharides

B) Protein;amino acids

What is one of the main differences between DNA and RNA? A) DNA uses four different bases than RNA does. B) RNA has two hydroxyl groups on the sugar, DNA has one. C) DNA has three phosphate groups, RNA has one. D) RNA does not contain the base cytosine.

B) RNA has two hydroxyl groups on the sugar, DNA has one.

Cytochrome c oxidase catalyzes the reaction that reduces molecular oxygen (two oxygen atoms) to two water molecules. The electrons are added sequentially, and during the process cytochrome c oxidase must bind the oxygen tightly in the active site. Why? A) If the oxygen escapes, it will bubble out as a gas and escape quickly. B) Superoxide radicals are formed as an intermediate, and are dangerous to the cell. C) Oxygen will bind to the electron-transport chain and reverse the pumping of protons. D) The escaped oxygen will form carbon monoxide and kill the cell.

B) Superoxide radicals are formed as an intermediate, and are dangerous to the cell.

64) You drop a handful of common table salt into a glass of water. Which of the following best describes what is happening inside the glass at the molecular level? A) Water and sodium form a covalent bond. B) The positively charged hydrogen ends of the water molecules are attracted to chloride ions. C) The positively charged hydrogen ends of the water molecules are attracted to sodium ions. D) Sodium and chloride ions form a covalent bond.

B) The positively charged hydrogen ends of the water molecules are attracted to chloride ions.

Which of the following is a reason why ATP hydrolysis has a negative ΔG0? A) ATP has a high concentration in cells. B) The removal of the phosphate is energetically favorable. C) The reverse reaction is extremely fast. D) The products have more free energy than the reactants.

B) The removal of the phosphate is energetically favorable. -The products of the ATP hydrolysis reaction—ADP and free phosphate—are more stable and have a lower free energy. Release of free phosphate is energetically favorable because it relieves the repulsion of the negative charges of the neighboring phosphate groups and the aqueous environment to make hydrogen bonds with the phosphate.

What is the role of activated carriers in cells? A) They are enzymes that catalyze biosynthetic reactions and make them feasible at the temperature of a cell. B) They capture energy from energy releasing reactions and transfer it to other reactions. C) They are enzymes that catalyze the reactions that break down foodstuffs for energy generation in the cell. D) They carry energy from anabolic reactions for use in catabolic reactions.

B) They capture energy from energy releasing reactions and transfer it to other reactions. - Activated carriers collect electrons from oxidation of molecules in catabolic reactions and transfer them to anabolic reactions that require electrons for the reduction of molecules.

33) What property of phospholipids makes them important in cell membranes? A) They contain nucleic acids. B) They have a polar end and a nonpolar end. C) They are an important energy carrier molecule. D) They are part of DNA. E) They are found only in animals.

B) They have a polar end and a nonpolar end.

Amino acids with side chains that contain −COOH groups, like those shown below, would be ___________ in the aqueous environment of a cell. A) nonpolar B) acidic C) basic D) hydrophobic

B) acidic

Why is sunlight the ultimate source of energy for nearly all living things on Earth? A) because the Earth makes a full rotation on it's axis, which provides light once a day B) because photosynthetic organisms produce food molecules using light energy C) because animals obtain heat energy from the sun, which keeps them alive D) because all animals must consume plants for obtaining energy

B) because photosynthetic organisms produce food molecules using light energy

Why is the presence of oxygen required for the citric acid cycle to operate? A) because oxygen combines with carbon from acetyl CoA to form the citric acid product CO2 B) because the NADH passes its electrons to oxygen in the electron transport chain to renew NAD+ C) because oxygen oxidizes several enzymes in the citric acid cycle D) because oxygen forms the water that is used in hydrolysis reactions in the citric acid cycle

B) because the NADH passes its electrons to oxygen in the electron transport chain to renew NAD+

11) Hydrolysis may be correctly described as the A) constant removal of hydrogen atoms from a carbohydrate. B) breaking of a compound into its subunits by using water to break the bond between monomers. C) removal of water from a polymer. D) heating of a compound in order to drive off its excess water and to concentrate its volume.

B) breaking of a compound into its subunits by using water to break the bond between monomers.

48) The human body must maintain a constant pH. In the blood, bicarbonate serves as a(n) ________ to help maintain the necessary pH. A) base B) buffer C) solvent D) acid

B) buffer

In oxidative phosphorylation in mitochondria, high-energy electrons are transferred to the electron-transport chain from activated carriers like NADH. Stage 1 of photosynthesis also uses an electron-transport chain to pump protons and make ATP. In this case, where do the high-energy electrons come from? A) NADPH B) chlorophyll C) ADP D) FADH2

B) chlorophyll

Which of the following shows protein organizational units in the correct order from smallest to largest? A) subunit < domain < complex B) domain < subunit < complex C) complex < domain < subunit D) complex < subunit < domain

B) domain < subunit < complex

Which of the following techniques of microscopy allows the observation of living cells (i.e. NOT fixed cells) ? A) scanning electron microscopy B) fluorescent microscopy C) transmission electron microscopy D) There are no microscopy techniques suitable for the observation of living cells

B) fluorescent microscopy

The inner membrane of the mitochondrion appears ________ because it provides __________. A) smooth; a smaller surface for the organization of proteins in respiration B) folded; a large surface area for staging energy production processes C) smooth; a large surface area for staging energy production processes D) folded; a smaller surface area for the organization of proteins in respiration

B) folded; a large surface area for staging energy production processes

The food molecule whose breakdown generates most of the energy for a majority of animal cells is A) sucrose B) glucose C) fat D) protein

B) glucose

Glycogen synthetase enzyme, which forms glycogen from glucose, is activated by excess A) ATP. B) glucose 6-phosphate. C) phosphate. D) pyruvate.

B) glucose 6-phosphate

Biochemical subcompartments that form inside the nucleus are distinct from their immediate surroundings because of the A) formation of a lipid membrane. B) high concentrations of interacting proteins and RNA. C) fusion of oil droplets. D) disassembly of scaffold proteins.

B) high concentrations of interacting proteins and RNA.

54) Complex, three-dimensional, tertiary structures of proteins result from A) ionic and hydrogen bonds B) hydrogen and disulfide bonds. C) disulfide bonds. D) hydrogen bonds. E) ionic bonds.

B) hydrogen and disulfide bonds.

40) Cell membranes are an example of a lipid bilayer. In this lipid bilayer, both the outside of the cell and the inside of the cell are ________ in nature. A) hydrophilic B) hydrophobic C) watery D) polar E) charged

B) hydrophobic

Which of the following occurs by bringing nonpolar surfaces together to exclude water? A) hydrogen bonds B) hydrophobic forces C) Van der Waals attractions D) electrostatic attractions

B) hydrophobic forces

When a ligand binds to an allosteric enzyme's regulatory site, it changes the activity of that enzyme by A) directly blocking the active site. B) inducing a conformational change. C) acting as a chaperone. D) denaturing the enzyme.

B) inducing a conformational change.

Protons are pumped across the mitochondrial inner membrane to accumulate in the A) mitochondrial matrix. B) intermembrane space. C) cytosol. D) electron-transport chain.

B) intermembrane space.

What is the fermentation product produced in an anaerobic muscle cell? A) ethanol B) lactic acid C) 1 ATP D) 1 ADP

B) lactic acid

Enzymes increase the speed of a chemical reaction because they A) increase the temperature to provide the necessary boost of energy. B) lower the activation energy needed to start the reaction. C) make the reaction more energetically favorable. D) make the reaction spontaneous.

B) lower the activation energy needed to start the reaction.

Which of the following accurately matches the types of filaments in the cytoskeleton with their cellular function? A) microtubules—cell movement; intermediate filaments—chromosome segregation; actin filaments—strength/support B) microtubules—chromosome segregation; intermediate filaments—strength/support; actin filaments—cell movement C) microtubules—cell movement; intermediate filaments—strength/support; actin filaments—chromosome segregation D) microtubules—strength/support; intermediate filaments—cell movement; actin filaments—chromosome segregation

B) microtubules—chromosome segregation; intermediate filaments—strength/support; actin filaments—cell movement

70) Adenosine triphosphate (ATP) is an example of a(n) A) protein. B) nucleotide. C) inorganic molecule. D) carbohydrate. E) lipid.

B) nucleotide.

The Golgi apparatus' main function is to A) make proteins for secretion B) package and modify proteins for secretion

B) package and modify proteins for secretion

A nucleotide is different from a nucleoside because a nucleotide has a A) nitrogen-containing base B) phosphate group(s) C) ribose sugar. D) deoxyribose sugar.

B) phosphate group(s)

71) A nucleotide is made of a A) phospholipid, sugar, and nitrogenous base. B) phosphate, sugar, and nitrogenous base. C) phosphate, protein, and nitrogenous base. D) phospholipid, sugar, and protein.

B) phosphate, sugar, and nitrogenous base.

A readily available source of energy that cells use to drive reactions is stored in the ___________ bond. A) phosphodiester B) phosphoanhydride C) hydrogen D) peptide

B) phosphoanhydride

What is the name used for a molecule in which two carbons of glycerol are attached to fatty acid chains, and the third carbon is attached to a phosphate group? A) triacylglycerol B) phospholipid C) steroid D) amphipathic

B) phospholipid

The first step of glycolysis uses one ATP molecule in order to A) transport glucose. B) phosphorylate glucose. C) breakdown sucrose. D) store glucose.

B) phosphorylate glucose.

18) Chitin is an example of a A) monomer. B) polysaccharide. C) triglyceride. D) nucleic acid. E) peptide.

B) polysaccharide.

11) An atom's nucleus is composed of A) protons only. B) protons and neutrons. C) protons and electrons. D) neutrons and electrons. E) neutrons only.

B) protons and neutrons.

12) The formation of ions involves the A) sharing of protons. B) gain or loss of neutrons. c D) sharing of electrons. E) gain or loss of protons.

B) protons and neutrons.

19) Free radicals are considered dangerous because they A) attack the atomic nucleus. B) steal electrons from other atoms, causing those atoms to become unstable. C) damage oxygen and cause it to become an antioxidant. D) emit dangerous radiation.

B) steal electrons from other atoms, causing those atoms to become unstable.

65) Your friend does a belly flop into a swimming pool. The stinging pain he feels is most likely due to 65) theA) pH of the water. B) surface tension of water (caused by the large number of hydrogen bonds that form between water molecules). C) hydrophobic nature of your friend's skin. D) fact that water is a good solvent.

B) surface tension of water (caused by the large number of hydrogen bonds that form between water molecules).

One piece of evidence indicating that chloroplasts evolved from engulfed photosynthetic bacteria is A) the presence of chlorophyll B) that they contain their own DNA C) the folded membrane D) that mitochondria were already present in the cell

B) that they contain their own DNA

The Michaelis constant (KM) of an enzyme is a measure of A) the rate at which the enzyme converts the substrate to product. B) the binding strength of enzyme to substrate. C) the energetic favorability of the reaction. D) the activation energy.

B) the binding strength of enzyme to substrate.

Archaea and bacteria are two separate domains of prokaryotes that were distinguished by examining A) their cell structures B) their DNA sequences C) the presence vs. absence of a nucleus D) the presence vs. absence of chloroplasts

B) their DNA sequences

The photosynthetic machinery is found in which of the compartments A) stroma B) thylakoid membrane C) inner membrane D) outer membrane

B) thylakoid membrane

What is the function of a kinase? A) to oxidize a molecule B) to add a phosphate group to a molecule C) to rearrange the bonds into an isomeric form D) to shift a chemical group from one position to another in a molecule

B) to add a phosphate group to a molecule

During glycolysis, the number of ATP consumed (per glucose molecule) is ___________, while the number produced is ___________. Group of answer choices A) one; two B) two; four C) six; thirty-six D) four; two

B) two; four

The technique that scientists used to determine that hemoglobin was a single large macromolecule rather than a loose conglomeration of small organic molecules was A) electron microscopy. B) ultracentrifugation. C) DNA sequencing. D) hydrolysis.

B) ultracentrifugation.

3) You are telling your friend that organic molecules are all made up of carbon backbones with 3) hydrogens. She doesn't understand how there can be so many different organic molecules if they all are made up of the same basic components. You explain that organic molecules A) vary because they possess different isotopes of carbon. B) vary because they possess different functional groups. C) are different because of the different types of hydrogen bonds that form. D) actually all have the same structure but differ in the number of electrons.

B) vary because they possess different functional groups.

5) Large biological molecules are synthesized by removing A) covalent bonds. B) water. C) peptides. D) oxygen. E) carbon.

B) water.

7. The human genome contains approximately how many genes? A. 46 B. 30,000 C. 100,000 D. 3,000,000,000

B. 30,000

8. What evidence suggests that the large amount of excess "junk" DNA in a genome may serve an important function? A. All organisms have excess "junk" DNA B. A portion of "junk" DNA is highly conserved in its DNA sequence among many different eukaryotic species.

B. A portion of "junk" DNA is highly conserved in its DNA sequence among many different eukaryotic species.

1. Which base pairs are found in DNA? A. A-C and T-G B. A-T and C-G C. A-G and C-T D. A-U and C-G

B. A-T and C-G

22. In the chromatin of interphase chromosomes, regions of the chromosome that contain genes being expressed are generally more compact, while those that contain quiescent genes are more generally more extended. A. True B. False

B. False

9. Eukaryotic chromosomes contain a single replication origin. A. True B. False

B. False

42. A cell can pass certain types of chromatin structure to daughter cells during cell reproduction. What molecules are key to this type of inheritance? A. DNA molecules B. Histone proteins C. RNA molecules D. Telomere E. Spindle microtubules

B. Histone proteins

13. What structure in an interphase cell contains ribosomal RNA and proteins for the formation of ribosomes? A. Chromatin B. Nucleolus C. Nuclear lamina

B. Nucleolus

16. Histone proteins pack DNA into a repeating array of DNA-protein particles called: A. heterochromatin. B. nucleosomes. C. euchromatin. D. nucleoli.

B. nucleosomes.

14. The DNA in eukaryotic chromosomes is folded into a compact form by interactions with: A. RNA. B. proteins. C. euchromatin. D. microtubules. E. centromeres.

B. proteins.

10. The structures that cap the ends of eukaryotic chromosomes are called: A. centromeres. B. telomeres. C. mitotic spindles. D. histones.

B. telomeres.

Choose the statement that is not true regarding the function of bacterial RNA polymerase. A. Bacterial RNA polymerase can transcribe along the DNA in either direction. B. Bacterial RNA polymerase does not require a primer. C. Bacterial RNA polymerase uses ribonucleoside triphosphates as substrates. D. Bacterial RNA polymerase does not require a helicase. E. Bacterial RNA polymerase makes more errors than DNA polymerase.

Bacterial RNA polymerase can transcribe along the DNA in either direction

A housekeeping gene is a gene whose cellular function is A. involved in removal of waste products from cells. B. turned off periodically for maintenance. C. important for processes found in all cell types. D. critical for specialized activities in a specific cell type.

A reporter gene is an experimentally engineered regulatory DNA sequence from a gene of interest that has been fused to a gene that encodes a protein that is easily observed experimentally. Why is this approach useful? A. It can provide information as to where a gene is expressed. B. It can provide information as to when a gene is expressed. C. It provides information into where and when a gene is expressed. D. It provides information on the binding interactions of the gene product.

Eukaryotic repressor proteins can decrease transcription using which of the following mechanisms? A. binding an operon and preventing polymerase binding B. recruiting a histone acetyltransferase complex to modify histones C. preventing the assembly of the transcription initiation complex D. attracting a chromatin remodeling complex to open chromatin at the site

Export of RNA from the nucleus requires the RNA to have which characteristic(s)? A. 5′ cap B. poly-A tail C. 5′ cap and poly-A tail D. introns

How do point mutations typically arise? A. chemical carcinogens B. radiation C. replication errors D. cell-division errors

If one end of a DNA strand has a phosphate group on it, the chemical group on the other end must be A. phosphate. B. carboxyl. C. hydroxyl. D. methyl.

Many transcriptional regulators function together to decide the expression level of a particular gene. This describes the concept of A. operons. B. repression. C. combinatorial control. D. activation.

Noncoding RNAs include all of the following EXCEPT A. rRNA. B. tRNA. C. mRNA. D. regulatory RNAs.

The transcription of an integrated retroviral DNA in the genome functions to supply what products for the replication virus? A. more RNA genome copies B. RNA for translation into protein for the viral coat/envelope C. more copies of the genome and protein for the viral coat/envelope D. RNA intermediates for direct integration into another location in the genome

The type of bond that holds together neighboring subunits in a single strand of DNA is a A. hydrogen bond. B. phosphoanhydride bond. C. phosphodiester bond. D. peptide bond.

Transplanting the nucleus of an epithelial cell into an egg cell lacking genetic information leads to the formation of A. another epithelial cell. B. a dead cell. C. a normally developing embryo. D. a hybrid cell that has characteristics of both embryonic cells and epithelial cells.

What is a defining difference between viruses and mobile genetic elements? A. Mobile genetic elements can insert into genomes; viruses cannot. B. Viruses sometimes use cell machinery to replicate; mobile genetic elements always use their own enzymes. C. Viruses can leave the cell and move to other cells and organisms; mobile genetic elements generally just move around the genome within in a cell. D. Mobile genetic elements do not use RNA intermediates in their transposition process, whereas viruses use RNA intermediates for replication.

What is the function of a topoisomerase in DNA replication? A. It coils the DNA for tighter packaging. B. It separates the DNA strands. C. It relieves the tension in DNA strands. D. It binds the template DNA to hold in place.

What is the relationship between genome size and organismal complexity? A. The more complex the organism, the larger the genome, without exception. B. The more complex the organism, the smaller the genome, without exception. C. More complex organisms generally have larger genomes but there are many notable exceptions. D. There is no relationship between genome size and organismal complexity, it is random.

Which of the following mechanisms for genetic change involves the acquisition of genetic material from another organism? A.gene duplication B. transposition C. horizontal transfer D. mutation

Which type of RNA is converted into protein for performing its cellular function? A. tRNA B. rRNA C. mRNA D. miRNA

38. The core histones are small, basic proteins that have a globular domain at the C-terminus and a long extended conformation at the N-terminus. Which of the following is not true of the N terminal "tail" of these histones? A It is subject to covalent modifications, B It extends out of the nucleosome core. C It binds to DNA in a sequence-specific manner. D It helps DNA pack tightly.

C It binds to DNA in a sequence-specific manner.

34. The process of sorting human chromosomes pairs by size and morphology is called karyotyping. A modern method employed for karyotyping is called chromosome painting. How are individual chromosomes "painted"? A with a laser B using fluorescent antibodies C using fluorescent DNA molecules D using green fluorescent protein

C using fluorescent DNA molecules

39. Although the chromatin structure of interphase and mitotic chromosomes is very compact, DNA-binding proteins and protein complexes must be able to gain access to the DNA molecule. Chromatin-remodeling complexes provide this access by __________________. A recruiting other enzymes B modifying the N-terminal tails of core histones C using the energy of ATP hydrolysis to move nucleosomes D denaturing the DNA by interfering with hydrogen-bonding between base pairs

C using the energy of ATP hydrolysis to move nucleosomes

32) Which of the following pairs has the most similar chemical properties to each other? 32) A) 12C and 28Si B) 1H and 22Na C) 12C and 14C D) 16O and 32S E) 1H and 2He

C) 12C and 14C

69) How many hydrogen bonds exist between a G-C base pair? A) 1 B) 2 C) 3 D) 4

C) 3

7) Iron is an important element in human body cells. If iron has an atomic number of 26, what does 7) this tell you about this element? A) An iron atom is unable to become an isotope. B) An iron atom has 13 protons and 13 neutrons. C) An iron atom has 26 protons. D) An iron atom has 13 electrons and 13 protons.

C) An iron atom has 26 protons.

58) What determines the cohesiveness of water molecules? A) Hydrophobic interactions B) Covalent bonds C) Hydrogen bonds D) Ionic bonds

C) Hydrogen bonds

6) What type of chemical reaction results in the breakdown of organic polymers into their respective subunits? A) Ionization B) Condensation C) Hydrolysis D) Oxidation

C) Hydrolysis

39) Which of the following results from a transfer of electron(s) between atoms (e.g., NaCl)? A) Nonpolar covalent bond B) Polar covalent bond C) Ionic bond D) Hydrogen bond E) Electron-proton interaction

C) Ionic bond

50) What is meant by the statement that water has a high specific heat? A) Water freezes easily. B) Water can heat up to only a certain temperature. C) It can absorb a lot of energy without changing temperature. D) The boiling point of water is low. E) It grows hot quickly.

C) It can absorb a lot of energy without changing temperature.

34) Lard is a solid fat at room temperature. What does this tell you about the triglycerides in lard? A) Lard is composed of unsaturated fats. B) The fats in lard are not organic molecules. C) Lard is composed of saturated fats. D) The fats in lard are mostly phospholipids.

C) Lard is composed of saturated fats.

Which of the following is a role of the cytoskeleton in plant cells? A) Intermediate filaments support chloroplast structure. B) Actin filaments guide cell movement. C) Microtubules form tracks for movement of cell components. D) Intermediate filaments form strong links to the plant cell wall.

C) Microtubules form tracks for movement of cell components.

2) If you examined the human body on a chemical composition basis, which of the following 2) combinations of elements would be most common? A) C, H, Ca, Cl B) O, C, P, S C) O, C, H, N D) O, C, N, Na E) C, N, Ca, S

C) O, C, H, N

55) The four polypeptides that are joined together to make functional hemoglobin represent which level of protein organization? A) Tertiary structure B) Primary structure C) Quaternary structure D) Secondary structure

C) Quaternary structure

38) Which of the following is an example of hydrogen bonding? A) The bond between H of one water molecule and H of a separate water molecule B) The bond between the H of a water molecule and H of a hydrogen molecule C) The bond between O of one water molecule and H of a separate water molecule D) The bond between O and H in a single molecule of water E) The bond between O of one water molecule and O of a separate water molecule

C) The bond between O of one water molecule and H of a separate water molecule

13) Dehydration synthesis involves the removal of a hydrogen ion and a hydroxyl ion. What happens next? A) The hydrogen ion becomes an isotope. B) A large polymer is split apart into small monomers. C) The hydrogen and hydroxyl ions combine to form water. D) A polysaccharide is released from a monosaccharide.

C) The hydrogen and hydroxyl ions combine to form water.

47) How do buffers work? A) They accept and release OH-. B) They monitor the blood pH. C) They accept and release H+. D) They convert H+ and OH- to water. E) They soak up extra acid and base.

C) They accept and release H+

44) Which of the following statements about lipids is incorrect? A) They are used for energy storage. B) They are large chains of nonpolar hydrocarbons. C) They are short chains of polar hydrocarbons. D) They are hydrophobic and water insoluble. E) They are primary component of cell membranes.

C) They are short chains of polar hydrocarbons.

37) Which statement is an accurate description of water molecules? 37)A) They are uncharged and nonpolar. B) They are charged and nonpolar. C) They are slightly charged and polar. D) They are ionically bonded.

C) They are slightly charged and polar.

How do the high-energy electrons of activated carriers contribute to forming the high-energy phosphate bonds of ATP? A) They are transferred directly to ADP to form ATP. B) They are passed to ATP synthase to power ATP synthesis. C) They are used by the electron-transport chain to make a proton gradient. D) They are pumped across the membrane to form an electron gradient.

C) They are used by the electron-transport chain to make a proton gradient.

Which of the following is true about amyloid protein structures? A) They always cause neurogenerative diseases. B) They are weak and brittle. C) They consist of stacked β sheets. D) They are made up of helical protein fibers.

C) They consist of stacked β sheets.

77) All animals need oxygen gas (O2) for their primary cellular-level functioning. Inside the cell, O2 is 90) split apart into oxygen atoms. Eventually, electrons that are flowing through the cell will be "received" by this oxygen. But first, the electrons combine with protons present in the cell to form a basic element that has a single proton and a single electron. Then this element combines with the oxygen to form a certain chemical compound. In this scenario, what chemical compound is produced when this element combines with oxygen? A) Ozone (O3) B) Bicarbonate (HCO3) C) Water (H2O) D) Carbon dioxide (CO2)

C) Water (H2O)

63) The specific heat of water is 10 times greater than that of iron. You place a metal pot full of water on the stove to heat it up. You touch the metal handle of the pot when the water is still only lukewarm. Which of the following best describes what happens? A) You find that the handle is cooler than the water in the pot. B) You find that both the water and the handle are the same temperature. C) You burn your finger and pull your hand away from the hot metal handle. D) You determine that metal pots full of water produce acids and bases.

C) You burn your finger and pull your hand away from the hot metal handle.

Which of the following is UNLIKELY to be hydrophilic? A) a salt that is held together with ionic bonds B) a molecule with a lot of polar covalent bonds C) a molecule with primarily nonpolar covalent bonds D) a molecule that forms hydrogen bonds with water

C) a molecule with primarily nonpolar covalent bonds

What is a protein family? A) a set of proteins that have the same number of domains B) a group of proteins from unrelated species C) a structurally related group of proteins D) a collection of proteins that have all been crystallized

C) a structurally related group of proteins

Which method is used for separating proteins based on specific interactions with other molecules? A) mass spectrometry B) gel electrophoresis C) affinity chromatography D) x-ray crystallography

C) affinity chromatography

The genes in the genome of an adult organism A) must all be expressed in all the cells of the organism for survival B) are mostly silenced after embryonic development is complete C) are expressed or silenced depending on whether a gene is needed in that cell type and environment D) are vastly different in composition depending on the cell type

C) are expressed or silenced depending on whether a gene is needed in that cell type and environment

A segment of DNA in the genome that is not a protein-coding gene A) is junk DNA left over from mistakes in evolution. B) is completely unimportant to the cell. C) can be used to regulate gene activity. D) must encode a functional RNA.

C) can be used to regulate gene activity.

20) An example of a structural polysaccharide is A) starch. B) glucose. C) cellulose. D) glycogen. E) maltose.

C) cellulose

Cellular respiration ___________ energy and produces ___________, whereas photosynthesis ___________ energy and produces ___________. A) consumes; oxygen + sugars; produces; water + carbon dioxide B) produces; oxygen + sugars; consumes; water + carbon dioxide C) consumes; water + carbon dioxide; produces; oxygen + sugars D) produces; water + carbon dioxide; consumes; oxygen + sugars

C) consumes; water + carbon dioxide; produces; oxygen + sugars

27) Polar covalent bonds form when A) more than one pair of electrons is shared. B) an acid and a base are combined. C) electrons are shared unequally between atoms. D) atoms from two molecules are repelling each other. E) ions are formed.

C) electrons are shared unequally between atoms.

22) The element carbon has atomic number 6. Carbon most likely A) donates two electrons to another atom. B) shares two electrons with another atom. C) forms four covalent bonds. D) forms ionic bonds with other atoms.

C) forms four covalent bonds.

67) Unlike a rock, a reptile can sit in the hot sunshine without its body temperature soaring quickly. This is because the water in its body A) has a low specific heat. B) is a poor solvent. C) has a high specific heat. D) is a good solvent.

C) has a high specific heat.

34) Polar molecules A) are always ions. B) have an equal distribution of electric charge. C) have an unequal distribution of electric charge. D) have an overall negative electric charge. E) have an overall positive electric charge.

C) have an unequal distribution of electric charge.

Which type of noncovalent interaction can involve either the polypeptide backbone or amino acid side chains? A) van der Waals attractions B) hydrophobic forces C) hydrogen bonds D) electrostatic interactions

C) hydrogen bonds

22) Lactose is a disaccharide of glucose and galactose, and its digestion requires the actions of the enzyme lactase. If lactose is eaten as part of the diet but is not digested by lactase, this sugar is then metabolized by bacteria in the intestine, leading to the symptoms of lactose intolerance. Lactose intolerance, therefore, results from a(n) A) lack of dehydration synthesis of lactose. B) inability of the body to produce lactose. C) lack of hydrolysis of lactose. D) low blood lactose level.

C) lack of hydrolysis of lactose.

30) Triglycerides are A) always composed of carbon rings. B) a main component of cellular membranes. C) made from glycerol and fatty acids. D) hydrophilic. E) polymers of amino acids.

C) made from glycerol and fatty acids.

Strong and specific associations between macromolecules or between an enzyme and its substrate are due to A) many strong covalent bonds. B) few strong covalent bonds. C) many weak noncovalent bonds. D) many strong noncovalent bonds.

C) many weak noncovalent bonds.

The proton flow through the transmembrane H+ carrier of ATP synthase results in A) bending of the carrier and stalk to produce mechanical force. B) moving ADP and Pi across the membrane into the enzyme active site. C) mechanical rotation that is converted into the chemical-bond energy of ATP. D) binding of the proton to ADP to enhance formation of the phosphate bond.

C) mechanical rotation that is converted into the chemical-bond energy of ATP.

If the products of a reaction have more free energy than the reactants, then that reaction is A) spontaneous. B) energetically favorable. C) not energetically favorable. D) physically impossible.

C) not energetically favorable.

52) The fact that salt dissolves in water is best explained by the) A) hydrophobic nature of salt. B) slightly charged nature of water molecules. C) polar nature of water molecules. D) hydrophobic nature of the water. E) ionic nature of water molecules.

C) polar nature of water molecules.

Self-replication of living cells occurs through the catalytic action of A) DNA B) RNA C) proteins D) nucleotides

C) proteins

Chlorophyll appears green because it __________ light. A) absorbs blue light. B) absorbs red light. C) reflects green light. D) reflects UV light.

C) reflects green light.

Chemical modifications like phosphorylation and acetylation of proteins occur on ___________ of amino acids and can affect interaction of proteins with other cell components or structures. A) amino groups B) carboxyl groups C) side chains D) peptide groups

C) side chains

Gluconeogenesis requires a total of ___________ ATP and GTP molecules combined. A) two B) four C) six D) eight

C) six

29) Cholesterol, testosterone, and estrogen are examples of A) proteins. B) waxes. C) steroids. D) nucleic acids. E) fatty acids.

C) steroids.

60) Sweating is a useful cooling mechanism for humans because water A) is an outstanding solvent. B) takes up a great deal of heat in changing from its solid state to its liquid state. C) takes up a great deal of heat in changing from its liquid state to its gaseous state. D) can exist in two states at temperatures common on Earth. E) ionizes readily.

C) takes up a great deal of heat in changing from its liquid state to its gaseous state.

16) Maltose is made from A) glucose and fructose. B) two peptides. C) two glucose molecules. D) glucose and galactose.

C) two glucose molecules.

Glycolysis produces ___________ ATP molecules, whereas the complete oxidation of glucose to water and carbon dioxide produces ___________ ATP molecules. A) two; ten B) four; thirty-four C) two; thirty D) four; twenty

C) two; thirty

2. What type of bond connects base pairs? A. Covalent bond B. Ionic bond C. Hydrogen bond

C. Hydrogen bond

17. What statement about nucleosomes is false? A. A nucleosome is a "bead" on a string of unfolded chromatin. B. A nucleosome produces a 3-fold packing ratio of DNA. C. Nucleosomes are found only in mitotic chromosomes. D. A nucleosome consists of DNA wrapped around 8 histone proteins, plus a short segment of linker DNA.

C. Nucleosomes are found only in mitotic chromosomes.

12. Telomeres: A. contain repeated nucleotide sequences that are required for the ends of chromosomes. B. allow duplicated chromosomes to become attached separated during M phase. C. cap the ends of the DNA molecule and prevent them from being recognized by the cell as broken DNA in need of repair. D. A and C only E. B and C only

C. cap the ends of the DNA molecule and prevent them from being recognized by the cell as broken DNA in need of repair.

Which of the following describes the Lac operon in E. coli when lactose, but not glucose, is present in the culture medium?

CAP, but not the Lac repressor, is bound to the Lac operon's regulatory DNA, and the Lac operon is expressed.

because hydrogen bonds hold the two strands of a DNA molecule together, the strands can be separated without breaking any covalent bonds. every unique DNA molecule "melts" at a different temperature. In this contect, Tm(melting temperature) is the point at which two strands seperate, or become denatured. which of the DNA sequences listed below has the highest melting temperature (Tm). Assume that they all begin as stable double-stranded DNA molecules. a. TTCTCATT b. TAAAGTCT c. CCCGCCGT d. CTAACTGG

CCCGCCGT

The major products of the citric acid cycle are

CO2 and NADH

Each molecule of acetyl-CoA entering the citric acid cycle produces two ___________ and four ___________.

CO2; activated carriers

If protein folding is determined by the sequence of amino acids in the polypeptide chain, why are chaperone proteins needed to assist folding in the cell?

Cartian proteins easily aggregate with other proteins FEEDBACK: All proteins can fold on their own without assistance due to the energetically favorable interactions between amino acid side chains and/or the polypeptide backbone. However, the cytoplasm is crowded and some proteins can form favorable interactions with other proteins before they have a chance to fold. These aggregates could impede proper folding.

The amino acid sequences below represent the sequences of transmembrane helices. The characteristics of α helices that form a channel are different from those that form a single transmembrane domain. Select the helix that forms a single transmembrane domain. (a) VGHSLSIFTLVISLGIFVFF (b) IMIVLVMLLNIGLAILFVHF (c) ILHFFHQYMMACNYFWMLCE (d) VTLHKNMFLTYILNSMIIII

Choice (b) is correct. The peptide sequences for options (a), (c), and (d) are amphipathic—that is, they contain a hydrophilic amino acid every 3-4 amino acids in the sequence. This indicates they may be part of a protein that makes a channel in the membrane, and they require hydrophobic amino acids on the surface that interacts with the lipid bilayer and a hydrophilic surface on the inside of the channel. Option (b) is the only sequence that is completely hydrophobic, indicating that it forms a helix in which all the side chains interact with the lipid bilayer.

While many prokaryotic cells have a single membrane bilayer, all eukaryotic cells have a complex system of internal membrane-bound compartments. How might it be advantageous for the cell to have these additional compartments?

Compartmentalization using intracellular membranes allows eukaryotic cells to separate a variety of cell processes. Although this requires a higher degree of coordination, the cell also gains a more stringent degree of control over these processes (examples include: the separation of transcription and translation; the separation of enzymes involved in protein modifications for secreted versus cytosolic substrates; the separation of proteolytic events in the lysosomes versus the cytosol; the separation of anaerobic metabolism in the cytosol and aerobic metabolism in the mitochondria).

how does phosphorylation of a protein affect its activity?

Could increase or decrease activity (FEEDBACK: Phosphorylation of amino acid side chains in a protein changes their charge to a negative charge. It could lead to changes in conformation of the protein, differences in binding to partners, and either increased or decreased activity of an enzyme. Thus, the effects of protein phosphorylation are particular to the protein itself.

At which step of gene expression can cells amplify the number of copies of a protein made from a single gene? A. transcription B. translation C. neither transcription nor translation D. both transcription and translation

How does methylation of histone tails affect the accessibility of DNA? A. It relaxes the chromatin to make DNA more accessible. B. It compacts the chromatin to make DNA less accessible. C. Histone methylation has no effect on chromatin. D. It can have different effects depending on the location.

Humans have an estimated 24,000 protein-coding genes in their genome, whereas Arabidopsis, a small plant, has 28,000 genes. Which statement best describes how the number of genes relates to the complexity of the organism? A. Organisms that are more complex always have more genes. B. Organisms with more genes are always less complex. C. There is no relationship between organismal complexity and number of genes. D. A higher number of genes generally correlates with complexity, with exceptions.

If a stretch of DNA on the parental strand of a replicating chromosome has the sequence 5′-AGCTCGATCGGCTA-3′, what will the sequence of the newly synthesized strand made from this stretch of template be? A. 5′-AGCTCGATCGGCTA-3′ B. 3′-AGCTCGATCGGCTA-5′ C. 5′-TCGAGCTAGCCGAT-3′ D. 3′-TCGAGCTAGCCGAT-5′

Protein concentration can be regulated by all of the steps listed EXCEPT A. nuclear export. B. RNA processing. C. mRNA stability. D. DNA replication.

Which of the following describes the chromosomal makeup of a somatic cell of a human biological male? A. 23 pairs of autosomes B. 23 pairs of autosomes + 1 Y chromosome C. 23 pairs of autosomes + 1 X chromosome + 1 Y chromosome D. 22 pairs of autosomes + 1 X chromosome + 1 Y chromosome

Which of the following is NOT a common source of DNA damage for cells in our bodies? A. UV light B. spontaneous loss of amino groups on cytosine C. replication fork problems D. soap

Which of the following is a difference between the mechanisms of DNA polymerase and RNA polymerase? A. The direction of polymerization for DNA polymerase is 5′ to 3′, but RNA polymerase is 3′ to 5′. B. DNA polymerase uses DNA as a template for making DNA copies; RNA polymerase uses RNA as a template for making RNAs. C. DNA polymerase uses the energy from the hydrolysis of the nucleotide triphosphates to drive the reaction; RNA polymerase uses reduced electron carriers. D. DNA polymerase needs a base-paired 3′ −OH for a polymerization reaction to occur; RNA polymerase can polymerize two nucleotides without a base-paired 3′ −OH.

Which of the following mechanisms describes how eukaryotic activator proteins can regulate chromatin packaging to enhance transcription? A. binding to enhancer regions to promote formation of the transcription initiation complex B. activating polymerase binding through contacts made in the activation region C. recruiting histone deacetylase complexes to remove acetyl groups from histones D. recruiting chromatin-remodeling complexes to eject or slide nearby nucleosomes

29. Which of the following sequences can fully base-pair with itself? A 5′-AAGCCGAA-3′ B 5′-AAGCCGTT-3′ C 5′-AAGCGCAA-3′ D 5′-AAGCGCTT-3′

D 5′-AAGCGCTT-3′

28. Which of the following chemical groups is not used to construct a DNA molecule? A five-carbon sugar B phosphate C nitrogen-containing base D six-carbon sugar

D six-carbon sugar

A folded protein structure with which free-energy (G) value would likely have the most stable conformation? A) 10 B) 5 C) 15 D) 1

D) 1

23) Sodium (Na), atomic number 11, has a tendency to lose an electron in the presence of chlorine. After losing the electron, Na has ________ protons in its nucleus. A) 10 B) 12 C) 22 D) 11 E) 21

D) 11 E) 21

48) Proteins are constructed using how many different amino acids? A) 4 B) 1,000 C) 100 D) 20 E) More than 5,000

D) 20

In the presence of high levels of ___________, the enzyme phosphofructokinase is inhibited. A) glucose B) ADP C) fructose D) ATP

D) ATP

20) Scientists recommend a diet rich in antioxidants to stay healthy. What occurs at the atomic level to 20) explain this recommendation? A) Antioxidants cause an increase in pH, which is necessary for neutrality in cells. B) Antioxidants steal electrons, which gives cells extra energy. C) Antioxidants are inert and do not interact with free radicals. D) Antioxidants prevent free radicals from attacking other atoms or molecules.

D) Antioxidants prevent free radicals from attacking other atoms or molecules.

56) When the acidic level of human blood increases, how is the proper balance of hydrogen ions (H +) 56) restored? A) H+ ion-donor levels increase. B) Carbonic acid eats up the extra OH- ions. C) Bicarbonate (HCO3-) releases H+ ions that combine with excess OH- ions to form H2O. D) Bicarbonate (HCO3-) accepts H+ ions and forms carbonic acid.

D) Bicarbonate (HCO3-) accepts H+ ions and forms carbonic acid.

5) Which four elements make up approximately 96% of living matter? 5) A) Carbon, phosphorus, hydrogen, sulfur B) Carbon, oxygen, calcium, sulfur C) Oxygen, hydrogen, calcium, sodium D) Carbon, hydrogen, nitrogen, oxygen E) Carbon, sodium, chlorine, magnesium

D) Carbon, hydrogen, nitrogen, oxygen

Which of the following is INCORRECT regarding how enzymes lower the activation energy of a reaction? A) Enzymes encourage the substrates to change shape toward a transition state that favors the reaction B) Enzymes align substrates to promote a reaction between them. C) Enzymes rearrange electrons in the substrates in a way that favors the reaction. D) Enzymes reduce the free energy of the products of the reaction.

D) Enzymes reduce the free energy of the products of the reaction.

7) Which of the following reactions is an example of dehydration synthesis? A) Glycogen → glucose subunits B) Peptide → alanine + glycine C) Fat → fatty acids + glycerol D) Glucose + galactose → lactose E) Cellulose → glucose

D) Glucose + galactose → lactose

26) When the level of glucose in your blood is high, your body is able to store excess glucose in the liver by forming glycogen. When blood glucose levels fall, this stored glucose can be released. Based on this information, which of the following is TRUE? A) Glycogen is a highly branched functional group that forms a larger glucose polymer. B) Glucose is a polysaccharide that can join to form the monosaccharide glycogen. C) Glucose is not an organic molecule, but glycogen is an organic molecule. D) Glycogen is a polysaccharide formed by joining excess monosaccharides of glucose.

D) Glycogen is a polysaccharide formed by joining excess monosaccharides of glucose.

28) Which of the following represents a molecule characterized by polar covalent bonding? 28) A) NaCl B) O2 C) H2 D) H2O E) CH4

D) H2O

51) Which of the following properties of water enable(s) it to function as a regulator of temperature for living organisms? (Hint: Think about what happens when you are sunbathing.) A) High heat of vaporization B) High specific heat C) High specific heat and high heat of vaporization D) High specific heat and low heat of vaporization E) Low specific heat

D) High specific heat and low heat of vaporization

73) Suppose you have discovered a new virus and have isolated its nucleic acids. What feature could 73) you look for to determine whether the nucleic acids of this virus are RNA or DNA? A) If it is RNA, there will be no adenine. B) If is RNA, it will contain deoxyribose. C) If it is DNA, the virus will not contain proteins. D) If it is RNA, it will contain ribose.

D) If it is RNA, it will contain ribose.

41) Which of the following biological molecules possess large nonpolar regions, making them insoluble in water? A) Carbohydrates B) Proteins C) Nucleic acids D) Lipids

D) Lipids

42) Which of the following groups is crucial to the structure and function of the sex hormones estrogen and testosterone? A) Proteins B) Carbohydrates C) Nucleic acids D) Lipids

D) Lipids

The citric acid cycle produces which activated carriers that transfer high-energy electrons to the electron-transport chain? A) NADPH and NADH B) NAD+ and FAD C) NADP and FAD D) NADH and FADH2

D) NADH and FADH2

61) In general, a substance that carries an electric charge can dissolve in water. Given this fact, which of the following would most likely NOT dissolve in water? A) Polar covalent molecules B) Ionic compounds C) NaCl D) Nonpolar molecules

D) Nonpolar molecules

74) Which of the following biological molecules are composed of monomer units containing a sugar, a phosphate group, and a nitrogen-containing base? A) Proteins B) Lipids C) Carbohydrates D) Nucleic acids

D) Nucleic acids

63) Your classmate is trying to keep all the facts about biological molecules straight. He asks you to explain how amino acids and proteins are related. What do you tell him? A) Amino acids are formed by joining together many proteins. B) Proteins are a portion of an amino acid. C) Proteins are chains of carbohydrates, and amino acids are a type of lipid. D) Proteins are made up of chains of amino acids.

D) Proteins are made up of chains of amino acids.

17) Sulfur is an essential element in the human body, and studying its characteristics is important in 17) understanding human physiology. Sulfur atoms have six electrons in their outer shell. Based on this information, which of the following is TRUE? A) Sulfur is an important isotope of hydrogen. B) Sulfur is inert. C) Sulfur has eight electrons in its outer shell. D) Sulfur can form important molecules using covalent bonds.

D) Sulfur can form important molecules using covalent bonds.

6) Imagine that you have been hired as a chemist and your first task is to examine a newly discovered 6) atom. The paperwork you are given states that its atomic number is 110. What does this mean? A) The atom contains 55 protons and 55 neutrons. B) The atom contains 55 electrons. C) The atom is an isotope. D) The atom contains 110 protons.

D) The atom contains 110 protons.

21) Which of the following best explains why a particular atom may not form compounds easily? 21) A) The atom has an uneven number of protons. B) The atom has seven electrons in its outer shell. C) The atom has no electrons. D) The atom's outer energy shells are completely full.

D) The atom's outer energy shells are completely full.

4) Phosphorus has an atomic number of 15, so what is the distribution of its electrons? A) The first, second, and third energy levels have 5 electrons each. B) The electron arrangement cannot be determined from the atomic number alone. C) The first energy level has 8 and the second has 7. D) The first energy level has 2, the second has 8, and the third has 5. E) The first energy level has 2 and the second has 13.

D) The first energy level has 2, the second has 8, and the third has 5.

44) An atom of nitrogen attracts electrons more strongly than an atom of hydrogen. In an ammonia molecule (NH3), which of the following best describes the electrical charge of the individual atoms? A) The nitrogen is slightly positive. B) The nitrogen becomes neutral. C) The hydrogens are strongly negative. D) The nitrogen is slightly more negative. E) Charges balance out and none of the atoms has any charge.

D) The nitrogen is slightly more negative.

79) In this scenario, how are the soap, dirt/oil, and water arranged at the molecular level? A) The soap is converted into a lipid that binds to the dirt/oil while repelling the water. B) The soap molecules encase the dirt/oil within a small droplet that has a hydrophobic exterior and a hydrophilic interior. C) Water and dirt/oil form covalent bonds inside a small droplet that has a soap -based outer membrane. D) The soap molecules encase the dirt/oil within a small droplet that has a hydrophilic exterior and a hydrophobic interior.

D) The soap molecules encase the dirt/oil within a small droplet that has a hydrophilic exterior and a hydrophobic interior.

78) In this scenario, what is the most likely procedure beer makers use to produce alcohol from starchy 97) grains? A) The starch is converted into glycogen, which is easier for the yeast to digest. B) The starch is converted into a polymer of many glucose molecules before being used. C) Water is used to break the bonds between glucose subunits in the starch, in a form of dehydration synthesis. D) The starch is broken down into mono- and/or disaccharides by hydrolysis before use.

D) The starch is broken down into mono- and/or disaccharides by hydrolysis before use.

43) Which of the following is TRUE about waxes? A) They are an important food source, and most animals have enzymes for breaking them down. B) They are a type of complex carbohydrate. C) They are unsaturated and most similar to proteins. D) They are saturated fats and are solid at normal outdoor temperatures.

D) They are saturated fats and are solid at normal outdoor temperatures.

30) If sulfur has an atomic number of 16, how many covalent bonds can it form with other atoms? 30) A) Four B) Six C) Zero D) Two E) Eight

D) Two

57) Which type of molecule is most abundant in a typical cell? A) Carbohydrate B) Nucleic acids C) Lipid D) Water E) Protein

D) Water

57) For ice to melt, it has to A) increase its property of cohesion. B) increase its heat of vaporization. C) become less dense. D) absorb heat from its surroundings.

D) absorb heat from its surroundings.

14) The formation of sodium chloride (NaCl) is the result of A) chemical unreactivity. B) repelling between the same charges. C) covalent bonding. D) attraction between opposite charges.

D) attraction between opposite charges.

The chemical reactions that take place in a cell, as compared to the chemistry in nonliving matter, primarily occur A) between simple molecules. B) in a hydrophobic environment. C) in extreme temperatures. D) between carbon-based molecules.

D) between carbon-based molecules.

9) In dehydration synthesis, the atoms that make up a water molecule come from A) oxygen. B) enzymes. C) only one of the reactants. D) both of the reactants. E) carbohydrates.

D) both of the reactants.

Mistakes in replicating the DNA of a cell before cell division A) have no consequence of the cell's survival B) always lead to reduced survival of the cell C) lead to increased survival of the cell D) can have positive, negative, or neutral effects

D) can have positive, negative, or neutral effects

How does phosphorylation of a protein affect its activity? A) always increases activity B) always decreases activity C) never affects activity D) could increase or decrease activity

D) could increase or decrease activity

Which method is most suitable for determining the three-dimensional structure of an extremely large integral membrane protein complex? A) NMR spectroscopy B) mass spectrometry C) x-ray crystallography D) cryoelectron microscopy

D) cryoelectron microscopy

9) Radioactive isotopes are biological tools that are often used to 9) A) build up a store of calcium in a cell. B) increase the pH of blood. C) measure the size of fossils. D) detect brain tumors and other important medical technologies.

D) detect brain tumors and other important medical technologies.

31) The part of the atom that has the greatest biological interest and interactions with other atoms is 31) the A) proton. B) innermost electron shell. C) neutron. D) electron.

D) electron.

49) The specific function of a protein is determined by the A) number of peptide bonds it contains. B) fatty acids that are joined together in the polypeptide. C) number of disulfide bonds. D) exact sequence of amino acids. E) hydrophilic head attached to the hydrophobic tail.

D) exact sequence of amino acids.

36) All of the following lipids or lipid components are hydrophobic EXCEPT A) unsaturated fats. B) waxes. C) fatty acid tails. D) fatty acid heads. E) saturated fats.

D) fatty acid heads.

52) All of the following are polysaccharides EXCEPT A) chitin. B) glycogen. C) starch. D) glucose.

D) glucose.

60) A denatured protein differs from a normal protein because it A) contains many disulfide bonds. B) is composed of nucleotides. C) does not contain amino acids. D) has lost its usual secondary and tertiary structures.

D) has lost its usual secondary and tertiary structures.

The main function of the nucleus is to A) provide energy for the cell B) allow cells to segregate their chromosomes C) make proteins using the genetic material D) house the DNA in a separate cell compartment

D) house the DNA in a separate cell component

13) If a certain atom has a tendency to lose two electrons, that atom can then become a(n) A) polar molecule. B) water molecule. C) isotope. D) ion.

D) ion.

45) HDL and LDL are different types of cholesterol found in the blood. These compounds are A) carbohydrates. B) proteins. C) nucleic acids. D) lipids.

D) lipids.

1) Prions are known to cause A) sickle cell anemia. B) the common cold. C) herpes. D) mad cow disease.

D) mad cow disease.

The fruit fly, Drosophila melanogaster (D. melanogaster) is an excellent model for studying fundamentals of development because A) the precise formation of each of their 959 body cells has been mapped. B) they are transparent and allow visualization of cell division and movement. C) they reproduce every 30 minutes on a plate. D) many of the genes involved in the development of the fruit fly are also found in humans.

D) many of the genes involved in the development of the fruit fly are also found in humans.

Which of the following chemical groups could confer nonpolar/hydrophobic characteristics on the region of a molecule in which it is found? A) phosphate groups (−PO32-) B) carboxyl group (−COOH) C) amino group (−NH2) D) methyl group (−CH3)

D) methyl group (−CH3)

The function of a _______ cell, which has a long, branched structure, requires many connections to be made with neighboring cells? A) egg B) fat C) yeast D) nerve

D) nerve

Which of the following correctly matches the cellular location with the production of ATP by oxidative phosphorylation in that cell type? A) chloroplasts—plants B) mitochondria—archaea C) cell wall—photosynthetic algae D) plasma membrane—bacteria

D) plasma membrane—bacteria

47) Enzymes are specialized ________ that catalyze chemical reactions within the body. A) nucleic acids B) lipids C) carbohydrates D) proteins

D) proteins

46) The group of biological molecules that are most diverse in function is A) nucleic acids. B) carbohydrates. C) lipids. D) proteins.

D) proteins.

Which of the following levels of protein structure involves the interaction of more than one polypeptide chain into a three-dimensional structure? A) primary B) secondary C) tertiary D) quaternary

D) quaternary

24) Carbon has atomic number 6. Carbon most likely A) shares neutrons. B) loses electrons. C) shares protons. D) shares electrons. E) loses protons.

D) shares electrons.

In addition to being converted to acetyl CoA for the citric acid cycle, pyruvate made during glycolysis can be used for A) membrane transport. B) synthesis of alanine. C) fermentation. D) synthesis of alanine and fermentation.

D) synthesis of alanine and fermentation.

Which of the following is a mobile electron carrier in the electron-transport chain? A) NADH dehydrogenase complex B) cytochrome c reductase complex C) cytochrome c oxidase complex D) ubiquinone

D) ubiquinone; also cytochrome c

Condensation reactions are energetically ___________ and hydrolysis reactions are energetically ___________. A) unfavorable; unfavorable B) favorable; favorable C) favorable; unfavorable D) unfavorable; favorable

D) unfavorable; favorable

Ionic bonds are ___________ than covalent bonds and are ___________ common in cells. A) stronger; more B) stronger; less C) weaker; more D) weaker; less

D) weaker; less

What is the relationship between ΔG and ΔG0? A) ΔG0 is the free-energy change at standard temperature. B) ΔG0 is the free-energy change at standard pressure. C) ΔG0 is the free-energy change at standard concentrations. D) ΔG0 is the free-energy change at standard temperature and concentrations.

D) ΔG0 is the free-energy change at standard temperature and concentrations.

Hydrogen bonding between N-H and C=O groups of every fourth amino acid within a polypeptide chain results in which type of folding pattern? A) antiparallel β sheet (A) B) parallel β sheet (B) C) amyloid structure (C) D) α helix (D)

D) α helix (D)

8) Carbon-14 is often used for carbon dating, where scientists measure the rate of carbon-14 decay to 8) determine the age of items. Carbon-14 contains six protons and eight neutrons. During the process of carbon-14 decay, one of its eight neutrons becomes a proton and an electron is emitted. Which of the following is the best explanation of what has occurred? A) The resulting atom is still carbon-14. B) An ionic bond has formed. C) The resulting atom has a more stable nucleus. D) The resulting atom is now a different element because the number of protons has changed.

D)The resulting atom is now a different element because the number of protons has changed.

6. Which of the following is true for most genes? A. A gene is a segment of DNA that contains the instructions for making a particular protein. B. A gene is a segment of DNA that contains the instructions for making a particular RNA. C. A gene is a region of DNA that controls a discrete hereditary characteristic of an organism. D. All of the above.

D. All of the above.

21. The core histone proteins have tails that can be chemically modified by what type of group? A. Acetyl B. Phosphate C. Methyl D. Any of the above

D. Any of the above

41. If the mottled coloring of calico cats is due to X-chromosome inactivation, which of the following statements will be TRUE? A. Calico cats can be male or female. B. Female calico cats will be the same color as their mother. C. The mottled color is due to X chromosomes repeatedly switching back and forth between active and inactive states during development. D. Calico cats with identical patterns will be rare. E. Coat color is determined by a single gene.

D. Calico cats with identical patterns will be rare. E. Coat color is determined by a single gene.

15. The complex of DNA and protein in chromosomes is called: A. centromeres. B. histone. C. centrosome. D. chromatin.

D. chromatin.

27. In a DNA double helix, _____________________. A. the two DNA strands are identical B. Purines pair with purines C. Thymines pair with cytosine D. the two DNA strands run antiparallel E. The nucleotides are ribonucleotides

D. the two DNA strands run antiparallel

lysozyme stabilizes the transition state and mediates the cleavage of what macromolecule strand? a. DNA b. RNA c. Oligosaccharide d. protein

DNA

Which of the following is a difference between the mechanisms of DNA polymerase and RNA polymerase?

DNA polymerase needs a base-paired 3'-OH for a polymerization reaction to occur; RNA polymerase can polymerize two nucleotides without a base-paired 3'-OH.

Protein concentration can be regulated by all of the steps listed EXCEPT

DNA replication

A stretch of amino acids in polypeptide chain that is capable of independently folding into a defined structure is called a?

Domain. ( A domain is a sequence of amino acids in a polypeptide chain that adopts a defined folding pattern based on the interactions of the side chains, as well as contributions from the polypeptide backbone molecules. This is distinct from a subunit, which is a term used for a single, complete polypeptide chain that can interact with other subunits to form a larger complex.

which of the following shows protein organized units int he correct order from smallest to largest

Domain< subunit< Complex A domain is a portion of an amino acid sequence that folds into three-dimensional structure and is the smallest of the organizational units. A subunit is a single, complete polypeptide chain and may be made up of one or more domains. two or more subunits can assemble into a complex.

51) A peptide bond forms between which of these groups? A) Hydroxyl and carboxyl B) Carboxyl and aldehyde C) Amino and aldehyde D) Phosphate and hydroxyl E) Carboxyl and amino

E) Carboxyl and amino

8) Which of the following best summarizes the relationship between dehydration reactions and hydrolysis? A) Dehydration reactions can occur only after hydrolysis. B) Hydrolysis creates monomers, and dehydration reactions destroy them. C) Hydrolysis creates polysaccharides, and dehydration creates monosaccharides. D) Dehydration reactions occur only in animals, and hydrolysis reactions occur only in plants. E) Dehydration reactions assemble polymers, and hydrolysis breaks them down.

E) Dehydration reactions assemble polymers, and hydrolysis breaks them down.

19) Where is glycogen stored in vertebrate animals? A) Teeth and bones B) Fat cells C) Pancreas and blood D) Brain and kidneys E) Liver and muscles

E) Liver and muscles

36) Hydrogen bonding can take place between a hydrogen atom and what other atom? A) Nitrogen B) Nitrogen, oxygen, and fluorine C) Fluorine D) Hydrogen E) Oxygen

E) Oxygen

59) The bonding of two amino acid molecules to form a larger molecule requires which of the following? A) Both removal of a water molecule and formation of a hydrogen bond B) Formation of a hydrogen bond C) Formation of a glycosidic bond D) Addition of a water molecule E) Removal of a water molecule

E) Removal of a water molecule

17) The fiber in your diet is actually A) protein. B) starch. C) glycogen. D) ATP. E) cellulose.

E) cellulose.

16) Most biological molecules are joined by A) hydrogen bonds. B) peptide bonds. C) disulfide bonds. D) ionic bonds. E) covalent bonds.

E) covalent bonds.

55) Water molecules are cohesive because they 55) A) make up 60% to 90% of an organism's body weight. B) contain protons. C) are repelled by nonpolar molecules. D) stick to other polar molecules. E) form hydrogen bonds.

E) form hydrogen bonds.

35) The hydrogen bond between two water molecules forms because water is A) nonpolar. B) a large molecule. C) hydrophobic. D) a small molecule. E) polar.

E) polar.

53) Hydrophilic molecules A) are repelled by water. B) do not readily dissolve in water. C) are neutral and nonpolar. D) form hydrogen bonds among themselves. E) readily dissolve in water.

E) readily dissolve in water.

68) DNA carries genetic information in its A) helical form. B) tertiary structure. C) phosphate groups. D) sugar groups. E) sequence of bases.

E) sequence of bases.

67) The "backbone" of a nucleic acid molecule is made of A) NAD+ and FAD. B) amino acids. C) lipids. D) ATP molecules. E) sugar and phosphate groups.

E) sugar and phosphate groups.

32) Fats and oils are made of A) two fatty acids and one carboxyl acid. B) three amino acids and one glycerol. C) one glycogen and two phospholipids. D) three glycerols and three fatty acids. E) three fatty acids and one glycerol.

E) three fatty acids and one glycerol.

What types of bonds are formed between histone proteins and DNA to form nucleosome core particles?

Electrostatic interactions

Which of the following is INCORRECT regarding how enzymes lower the activation energy of a reaction?

Enzymes reduce the free energy of the products of the reaction. (FEEDBACK: Enzymes lower activation energy of a reaction by promoting changes in the substrate that will encourage the reaction to occur. This can include changes in shape, alignment of two substrates, or changes in the electron density to encourage bond breakage and formation. Enzymes do not change the overall free energy of the reaction.)

Why do cells use enzymes to harvest energy from food molecules rather than by direct oxidation?

Enzymes transfer energy from food to carrier molecules in small steps.

Which region is most likely to contain the highest density of genes?

Euchromatin

68) Isotopes are atoms of the same element that have different numbers of protons.

FALSE

71) The attractive force that holds two or more water molecules together is an example of an ionic bond.

FALSE

75) Most liquids become less dense upon solidification, but water is different in that it becomes denser when it solidifies.

FALSE

77) Phospholipids have hydrophilic tail regions and hydrophobic head regions.

FALSE

(T/F) Eukaryotic promoters always require all four core promoter elements (-35, -30, start site, and +30) in order for RNA polymerase to initiate transcription.

False

(T/F)Activation of the Polycomb complex is associated with euchromatin formation and gene silencing.

False

Oxygen, hydrogen, carbon, and nitrogen atoms are enriched in the cells and tissues of living organisms. The covalent bond geometries for these atoms influence their biomolecular structures. Match the elements on the left with the bond geometries illustrated on the right. Some elements assume more than one bond geometry. A. oxygen B. carbon C. nitrogen

Figure A2-29

A. What is the pH of pure water? B. What concentration of hydronium ions does a solution of pH 8 contain? C. Complete the following reaction: CH3COOH + H2O ↔ __________. D. Will the reaction in (C) occur more readily (be driven to the right) if the pH of the solution is high?

Figure A2-37 A. pH 7 B. 10-8 M C. CH3COO- + H3O+ D. Yes. If the pH is high, then the concentration of hydronium ions will be low. Therefore the rightward reaction, which produces hydronium ions, will be favored.

this histone protein is responsible for condensing packing and linking nucleosomes to form a condensed chromatin fiber? a. H2A b. H2B C. H1 D. H4 E. all of the above

Which enzymatic activities are typically associated with the Trithorax complex? (choose all correct answers, no partial credit)

H3K27 demethylase H3K4 methylase

which type of noncovalent interaction can involve either the polypeptide backbone or amino acid side chains?

Hydrogen bonds. FEEDBACK: The backbone of the polypeptide consists of uncharged polar covalent bonds. Because the bonds in the backbone are neither charger nor hydrophobic (i.e. nonpolar), hydrophobic forces and electrostatic interactions do not involve the backbone. Hydrogen bonds, however, are formed between atoms in the polar covalent bonds found in both amino acid side chains and in the carboxyl group and amino groups of the polypeptide backbone.

Match each term related to the structure of nucleic acids (A-I) with one of the descriptions provided. A. base B. glycosidic bond C. nucleoside D. nucleotide E. phosphoanhydride bond F. phosphoester bond G. ribose H. phosphodiester bond I. deoxyribose ____ the linkage between two nucleotides ____ the linkage between the 5′ sugar hydroxyl and a phosphate group ____ the nitrogen-containing aromatic ring ____ five-carbon sugar found in DNA ____ sugar unit linked to a base ____ linkage between the sugar and the base ____ linkages between phosphate groups ____ sugar linked to a base and a phosphate ____ five-carbon sugar found in RNA

H—the linkage between two nucleotides F—the linkage between the 5′ sugar hydroxyl and a phosphate group A—the nitrogen-containing aromatic ring I—five-carbon sugar found in DNA C—sugar unit linked to a base B—linkage between the sugar and the base E—linkages between phosphate groups D—sugar linked to a base and a phosphate G—five-carbon sugar found in RNA

Indicate whether the molecules below are inorganic (I) or organic (O). A. glucose B. ethanol C. sodium chloride D. water E. cholesterol F. adenosine G. calcium H. glycine I. oxygen J. iron K. phospholipid

Indicate whether the molecules below are inorganic (I) or organic (O). A. O B. O C. I D. I E. O F. O G. I H. O I. I J. I K. O

In bacterial cells, the tryptophan operon encodes the genes needed to synthesize tryptophan. What happens when the concentration of tryptophan inside a cell is high?

It activates the tryptophan repressor, which shuts down expression of the tryptophan operon.

Many antibiotics work by inhibiting bacterial protein synthesis. Investigators have isolated a promising new compound and wish to determine its mechanism of action. Using a cell-free translation system similar to the ones originally used to deduce the genetic code, the researchers incubate their drug with the synthetic polynucleotide 5'-AUGUUUUUUUUU.In the absence of the drug, this polynucleotide directs the synthesis of the peptide Met-Phe-Phe-Phe. When the drug is added, only the peptide Met-Phe is produced. Based on this observation, which is most likely the mechanism of action of this potential new antibiotic?

It blocks translocation of the large ribosomal subunit, preventing the movement of peptidyl-tRNA from the A site to the P site of the ribosome.

How does methylation of histone tails affect the accessibility of DNA?

It can have different effects depending on which amino acid of the histone tail is methylated

It can provide information into where and when a gene is expressed.

An RNA molecule (for example, rRNA or tRNA) within a cell can fold into complex three-dimensional shapes for which reason?

It is single-stranded.

It provides information into where and when a gene is expressed.

Shown here is a gene with the direction of transcription noted. How does the RNA polymerase know which strand to use as a template for the RNA, and which strand would it choose in this case?

It would use the bottom strand because the promoter sets the direction and the polymerase moves from 3' to 5' along the template strand.

On the N-terminal tail of histone 3, which two lysines can either acetylated or methylated? (choose the two correct answers that were discussed in class, no partial credit)

K9 K27

The technique whereby human chromosomes are stained and identified is called a

Karyotype

The maltose operon contains genes that code for proteins that catabolize the disaccharide maltose. Similar to the Lac operon, which is only efficiently transcribed in the presence of lactose, the maltose operon is only efficiently transcribed in the presence of maltose. How might induction of the maltose operon in response to maltose be achieved?

Maltose removes a repressor from an operon with an efficient promoter. Maltose causes an activator to bind an operon with an inefficient promoter.

Although membrane proteins contribute roughly 50% of the total mass of the membrane, there are about 50 times more lipid molecules than there are protein molecules in cellular membranes. Explain this apparent discrepancy.

Membrane proteins are much larger molecules than the membrane lipids. Thus, fewer are required to represent the same total mass contributed by the lipid components of the membrane. By this estimation, the molecular weight of the average membrane protein is 50 times that of the average membrane lipid.

What is the relationship between genome size and organismal complexity?

More complex organisms generally have larger genomes but there are many notable exceptions.

What is the benefit of protein synthesis in polyribosomes?

More protein can be produced from a single RNA

What is the benefit of protein synthesis in polyribosomes?

More protein can be produced from a single RNA.

Which of the following has a higher concentration in the cell to allow it to be available to accept electrons from oxidation of food molecules?

NAD+

The citric acid cycle produces which activated carriers that transfer high-energy electrons to the electron-transport chain?

NADH and FADH2

If cells were undergoing glycolysis but could not carry out fermentation, what products would build up in the cytosol?

NADH and pyruvate

Which of the following has the lowest electron affinity?

NADH dehydrogenase complex

Thermal motion promotes lateral position exchanges between lipid molecules within a monolayer. In an artificial bilayer, this movement has been estimated to be ~2 μm/second. This represents the entire length of a bacterial cell. Do you expect the lateral movement of a lipid molecule within a biological membrane to be equally fast? Explain your answer.

No. Although the rate of movement may be similar, it will most likely be slower in a biological membrane. An artificial bilayer is primarily phospholipids. Biological membranes contain a large number of protein components and specialized membrane domains that could limit the rate of lateral diffusion.

It is now a routine task to determine the exact order in which individual subunits have been linked together in polynucleotides (DNA) and polypeptides (proteins). However, it remains difficult to determine the arrangement of monomers in a polysaccharide. Explain why this is the case.

Nucleotides and amino acids have an intrinsic directionality, and the mechanism by which monomers are added into a growing polymer is always the same. This yields a linear polymer with the same directionality as the monomers. Polysaccharides are produced by linking monosaccharides together. The monosaccharides can be either added directly or modified to produce various derivatives before addition. Beyond this, there are multiple sites on each monosaccharide where addition can occur, producing highly complex, branched polymers.

Silicon is an element that, like carbon, has four vacancies in its outer electron shell and therefore has the same bonding chemistry as carbon. Silicon is not found to any significant degree in the molecules found in living systems, however. Does this difference arise because elemental carbon is more abundant than silicon? What other explanations are there for the preferential selection of carbon over silicon as the basis for the molecules of life?

On the basis of Figure 2-4 in your textbook, silicon is actually more abundant in the Earth's crust than carbon, so this is not likely to be the reason that carbon was used preferentially. Carbon might have been the element of choice in living systems because it is lighter than silicon and forms shorter covalent bonds with other elements. Shorter bonds are typically stronger and more stable.

As a protein is made, the polypeptide is in an extended conformation, with every amino acid exposed to the aqueous environment. Although both polar and charged side chains can mix readily with water, this is not the case for nonpolar side chains. Explain how hydrophobic interactions may play a role in the early stages of protein folding, and have an influence on the final protein conformation.

One reason that nonpolar groups are excluded from an aqueous environment is that a hydrophobic surface would organize water into a highly structured network of hydrogen bonds, which is energetically unfavorable. So, you would expect that nonpolar amino acids would group together early, forming "hydrophobic pockets," while the polar and charged side chains remain at the interface of the surrounding solution. In the final, folded protein, most of the nonpolar amino acids will remain buried inside the protein. This fold is more stable because nonpolar atoms are prevented from contact with water and remain in contact with each other.

At what site does the charged initiator tRNA first bind on the ribosome?

P site

The type of bond that holds together neighboring subunits in a single strand of DNA is a

Phosphodiester bond

Which of the following is true about "junk DNA"?

Portions of junk sequence are conserved between species and thus may be functional.

What is the name of the complex that degrades proteins that have reached the end of their lifespan, are damaged or are misplaced?

Proteasomes

For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below. Not all words or phrases will be used; each word or phrase should be used only once. Proteins are ______________ built from amino acids, which each have an amino group and a _____________ group attached to the central _______________. There are twenty possible _______________ that differ in structure and are generally referred to as "R." In solutions of neutral pH, amino acids are _______________, carrying both a positive and negative charge. When a protein is made, amino acids are linked together through _______________, which are formed by condensation reactions between the carboxyl end of the last amino acid and the ___________________ end of the next amino acid to be added to the growing chain. amino ionized polypeptides α-carbon length protein carbon noncovalent R group carboxyl peptide bonds side chains hydroxide

Proteins are polypeptides built from amino acids, which each have an amino group and a carboxyl group attached to the central α-carbon. There are twenty possible side chains that differ in structure and are generally referred to as "R." In solutions of neutral pH, amino acids are ionized, carrying both a positive and negative charge. When a protein is made, amino acids are linked together through peptide bonds, which are formed by condensation reactions between the carboxyl end of the last amino acid and the amino end of the next amino acid to be added to the growing chain.

which of the following levels of protein structure involves the interaction of more that one polypeptide chain into a three dimensional structure?

Quaternary (primary structure is the linear order of amino acids in a polypeptide chain. The secondary structure is the formation of organized arrangements to form segments like a(alpha) helices and Beta sheets. The tertiary structure is ht overall three-dimensional shape of a protein. The quaternary structure is the assembly of multiple folded polypeptide chain into. larger complex.

Which nucleic acid often base pairs with itself to fold into complex three-dimensional shapes in the cell?

RNA

Which nucleic acid often forms intramolecular (within the same molecule) base pairs with itself to fold into complex three-dimensional shapes in the cell?

RNA

Which of the following properties could help RNA be both an information storage unit and a self-replicating molecule?

RNA can act as a template for making copies of itself.

The splicing of introns out of an mRNA molecule is catalyzed by

RNA molecules that base pair with the splice sites to promote intron removal

The splicing of introns out of an mRNA molecule is catalyzed by:

RNA molecules that base pair with the splice sites to promote intron removal.

The splicing of introns out of an mRNA molecule is catalyzed by

RNA molecules that base pair with the splice to promote intron removal

Why does RNA polymerase make more mistakes than DNA polymerase?

RNA polymerase does not have a proofreading activity

Why does RNA polymerase make more mistakes than DNA polymerase?

RNA polymerase does not have proofreading activity.

Three different membrane components are shown in Figure Q11-10. Using the list below, identify the three components, and label the chemical groups indicated. A. glycerol B. sugar C. phospholipid D. glycolipid E. sterol F. unsaturated hydrocarbon G. saturated hydrocarbon H. sterol polar head group

See Figure A11-10.

A small membrane vesicle containing a transmembrane protein is shown in Figure Q11-31. Assume that this membrane vesicle is in the cytoplasm of a cell. Figure Q11-31 A. Label the cytosolic and noncytosolic faces of the membrane vesicle. This membrane vesicle will undergo fusion with the plasma membrane. B. Sketch the plasma membrane after vesicle fusion, indicating the new locations of the vesicle membrane and the transmembrane protein carried by the membrane vesicle. C. On your drawing for B, label the original cytosolic and noncytosolic faces of the vesicle membrane as it resides in the plasma membrane. Also label the extracellular space and the cytosol. Indicate the N- and C-terminus of the inserted transmembrane protein.

See Figure A11-31A.

Band 3 protein is important for erythrocyte shape and cortical flexibility. It participates in multiprotein complexes that include ankyrin and spectrin. There are three major populations of Band 3 in the plasma membrane: (1) unassociated with the cortex, with lateral diffusion limited only by spectrin fibers; (2) associated with spectrin fibers; and (3) associated with the actin junctional complex. Figure Q11-61 A. Redraw a portion of the erythrocyte cortex shown in Figure Q11-61, and indicate where you expect to find Band 3 protein, based on the description of the three major populations (label them 1, 2, and 3). B. Draw the single-particle tracking (SPT) profile you may expect to observe for each of these three populations. Explain your reasoning. Defects in any of the membrane proteins that participate in the multiprotein junctional complexes can disrupt the overall cell morphology. These erythrocyte pathologies are characterized by loss of the normal biconcave disc morphology and early clearance from the bloodstream. C. You have a patient who carries a mutation in the spectrin gene. The defect interferes with interactions between spectrin and Band 3. Consider your answer from part B and redraw SPT profiles for Band 3 populations as you expect to see them in the erythrocytes of your patient. Explain your reasoning.

See Figure A11-61 Figure A11-61 B. The lateral movement of populations 2 (dark gray) and 3 (black) would be fairly restricted by their association with spectrin fibers and the junctional complex, respectively. The lateral movement of population 1 (light gray) should be rapid, but contained within the particular region defined by spectrin fibers. Based on these parameters, potential SPT profiles are drawn below. C. Without the interaction with spectrin, it is likely that the Band 3 proteins that made up populations 2 and 3 will no longer be found associated with the junctional complex or the spectrin fibers. This implies that the majority of Band 3 molecules would be able to move rapidly through the membrane, restricted only by the spectrin fibers (essentially becoming part of population 1).

Chemical modification likes phosphorylation and acetylation of proteins occur on ________ of amino acids and can affect interaction of proteins with other cell components or structures?

Side Chains. (FEEDBACK: The chemical modification of phosphorylation and acetylation occurs on the side chain of the amino acid and can affect how proteins interact with other proteins or components of the cell. This effect can occur through the direct alteration of binding sites if the phosphorylation and acetylation occur on an amino acid in a binding site, or through a conformational change that indirectly alters the binding site.)

What is false regarding codons in mRNA molecules? A. Codons in mRNAs bind to complementary anticodons in tRNAs. B. Some codons do not code for amino acids. C. In some cases, several different codons code for the same amino acid. D. Some codons code for more than one amino acid. E. All codons contain three nucleotides

Some codons code for more than one amino acid.

The Drosophila regulatory segment that defines the location of Eve stripe 2 contains binding sites for four different transcription regulators: two repressors (Giant and Krüppel) and two activators (Bicoid and Hunchback). For Eve to be efficiently expressed in stripe 2, both repressors must be absent and both activators present. What would you expect to see in flies that lack the gene that encodes Bicoid? (Assume that Bicoid does not influence the expression of Hunchback, Giant, or Krüppel.)

Stripe 2 would become fainter

Selenium (Se) is an element required in the human body in trace amounts. Selenium is obtained through the diet and levels of selenium found in food depend greatly on the soil where it is grown. Once ingested and absorbed as selenate, it can become incorporated into a small number of polypeptides. These selenoproteins are formed when selenium replaces an element that is found in two of the twenty "standard" amino acids. Using your knowledge of atomic structure, the periodic table in Figure 2-7, and the structure of amino acids found in Panel 2-5, deduce which two amino acids may be converted to "seleno" amino acids and used to make selenoproteins.

Sulfur is the only element found exclusively in two of the twenty amino acids. This element is located directly above selenium in the periodic table, indicating that these elements have the same number of electrons in their outer shell and both prefer to form bonds with other atoms to fill their outer orbital. If selenium instead of sulfur is incorporated into cysteine or methionine, the altered "seleno" amino acids will be produced (selenocysteine and selenomethionine). We can expect that this substitution will alter the nature of the proteins in which these amino acids are incorporated because selenium is a larger atom than sulfur.

Superoxide radicals are formed as an intermediate, and are dangerous to the cell.

69) Every atom of the same element has an equal number of electrons and protons.

TRUE

70) Acids have pH values below 7, whereas bases have pH values above 7.

TRUE

72) When water freezes, stable hydrogen bonds form between the water molecules that create an open, six-sided (hexagonal) arrangement.

TRUE

73) Water surface tension is a result of the cohesive nature of water molecules.

TRUE

74) To maintain a constant pH, buffers act to either accept or release H+.

TRUE

76) Functional groups determine the characteristics and chemical reactivity of organic molecules.

TRUE

Which characteristic of a replicating RNA polymerase allows multiple transcripts to be made simultaneously from the same region of DNA?

The RNA transcript dissociates from the DNA template immediately once complete.

What can happen if heterochromatin spreads inappropriately into an area with active genes?

The active genes can become silenced

Shown below is the ATP hydrolysis cycle of a motor protein. What sentence BEST describes the state of the motor protein in "C"?

The hydrolysis of ATP and ADP caused a conformational change in the protein. (A) is the state where no ATP or ADP is bound. The protein is bound to the filament with one of its two filament-binding domains, while the other binding domain is unbound. (B) shows that upon ATP binding, a conformational change moves the unbound domain forward one step to interact with the filament. In (C), ATP is hydrolyzed to ADP, creating a conformational change to release the rear filament-binding domain and bring it forward.)

Why is the oxidation of NADPH energetically favorable?

The oxidized form of NADPH is more stable than the reduced form.

The protons could be also captured from the intermembrane space and released back into the matrix.

Which of the following is a reason why ATP hydrolysis has a negative ΔG0?

The removal of the phosphate is energetically favorable.

The specialized functions of different membranes are largely determined by the __________________ they contain. Membrane lipids are __________________ molecules, composed of a hydrophilic portion and a hydrophobic portion. All cell membranes have the same __________________ structure, with the __________________ of the phospholipids facing into the interior of the membrane and the __________________ on the outside. The most common lipids in most cell membranes are the __________________. The head group of a glycolipid is composed of __________________. amphipathic hydrophobic phosphatidylserine cholesterol lipid bilayer phospholipids fatty acid tails lipid monolayer proteins glycolipids lipids sterols hydrophilic head groups phosphatidylcholine sugars

The specialized functions of different membranes are largely determined by the proteins they contain. Membrane lipids are amphipathic molecules, composed of a hydrophilic portion and a hydrophobic portion. All cell membranes have the same lipid bilayer structure, with the fatty acid tails of the phospholipids facing into the interior of the membrane and the hydrophilic head groups on the outside. The most common lipids in most cell membranes are the phospholipids. The head group of a glycolipid is composed of sugars.

The cell is able to harvest energy from various processes in order to generate ATP molecules. These ATPs represent a form of stored energy that can be used later to drive other important processes. Explain how the cell can convert the chemical energy stored in ATP to generate mechanical energy, for example changing the shape of a protein.

The terminal phosphate group is typically hydrolyzed and the energy released from this chemical bond is often "reinvested" to generate a new bond that links the phosphate group to a protein. This addition of a phosphate group can cause a change in the protein's conformation. This conformational change is usually associated with change in function or transient interactions with other macromolecules, generating a domino effect within the cell.

There are several ways that membrane proteins can associate with the cell membrane. Membrane proteins that extend through the lipid bilayer are called __________________ proteins and have __________________ regions that are exposed to the interior of the bilayer. On the other hand, membrane-associated proteins do not span the bilayer and instead associate with the membrane through an α helix that is __________________. Other proteins are __________________ attached to lipid molecules that are inserted in the membrane. __________________ membrane proteins are linked to the membrane through noncovalent interactions with other membrane-bound proteins. amphipathic hydrophilic noncovalently cortical hydrophobic peripheral covalently integral transmembrane detergent micelle unfolded

There are several ways that membrane proteins can associate with the cell membrane. Membrane proteins that extend through the lipid bilayer are called transmembrane proteins and have hydrophobic regions that are exposed to the interior of the bilayer. On the other hand, membrane-associated proteins do not span the bilayer and instead associate with the membrane through an α helix that is amphipathic. Other proteins are covalently attached to lipid molecules that are inserted in the membrane. Peripheral membrane proteins are linked to the membrane through noncovalent interactions with other membrane-bound proteins.

What is true of bacterial mRNAs?

They are transcribed and translated simultaneously.

What is true of eukaryotic mRNAs?

They are translated after they are exported from the nucleus.

How do the high-energy electrons of activated carriers contribute to forming the high-energy phosphate bonds of ATP?

They are used by the electron-transport chain to make a proton gradient.

What is the role of activated carriers in cells?

They capture energy from energy releasing reactions and transfer it to other reactions.

The process of gene expression always involves which process(es) described in the dogma?

Transcription

(T/F) Each eukaryotic chromosome must contain the following DNA sequence elements: one centromere, two telomeres, and multiple origins of replication.

True

In RNA, which nitrogenous base will pair with the base A?

The relative strengths of covalent bonds and van der Waals interactions remain the same when tested in a vacuum or in water. However, this is not true of hydrogen bonds or ionic bonds, whose bond strengths are lowered considerably in the presence of water. Explain these observations.

We estimate bond strengths by measuring the amount of energy needed to break them. As explained in Panel 2-7 (p.78-79), in an aqueous solution, water can form hydrogen bonds with any polar molecules that are capably of forming hydrogen bonds with each other. This formation of bonds with water takes away from the net energy that would be gained from the molecules forming hydrogen bonds with each other, as they would in a vacuum. Similarly, water forms favorable electrostatic interactions with ions, thereby greatly weakening the ionic bonds that form between positive and negative ions in a vacuum (see Panel 2-7). Thus, for example, solid table salt (NaCl) readily dissociates in water, producing separate Na+ and Cl- ions as it dissolves. In contrast, covalent bonds and van der Waals attractions have an intrinsic bond strength that is independent of the aqueous environment, because changes in water molecule associations are not involved in the formation of these two types of bonds.

For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below. Not all words or phrases will be used; each word or phrase should be used only once. Whereas ionic bonds form a(n) __________________, covalent bonds between atoms form a(n) __________________. These covalent bonds have a characteristic bond __________________ and become stronger and more rigid when two electrons are shared in a(n) __________________. Equal sharing of electrons yields a(n) __________________ covalent bond. If one atom participating in the bond has a stronger affinity for the electron, this produces a partial negative charge on one atom and a partial positive charge on the other. These __________________ covalent bonds should not be confused with the weaker __________________ bonds that are critical for the three-dimensional structure of biological molecules and for interactions between these molecules. charge length polar covalent molecule salt double bond noncovalent single bond ionic nonpolar weight

Whereas ionic bonds form a salt, covalent bonds between atoms form a molecule. These covalent bonds have a characteristic bond length and become stronger and more rigid when two electrons are shared in a double bond. Equal sharing of electrons yields a nonpolar covalent bond. If one atom participating in the bond has a stronger affinity for the electron, this produces a partial negative charge on one atom and a partial positive charge on the other. These polar covalent bonds should not be confused with the weaker noncovalent bonds that are critical for the three-dimensional structure of biological molecules and for interactions between these molecules.

What is the "central dogma"?

Within the cell, genetic information flows from DNA to RNA to protein.

A covalent bond between two atoms is formed as a result of the ______________. (a) sharing of electrons. (b) loss of electrons from both atoms. (c) loss of a proton from one atom. (d) transfer of electrons from one atom to the other.

Although covalent bonds are 10-100 times stronger than noncovalent interactions, many biological processes depend upon the number and type of noncovalent interactions between molecules. Which of the noncovalent interactions below will contribute most to the strong and specific binding of two molecules, such as a pair of proteins? (a) electrostatic attractions (b) hydrogen bonds (c) hydrophobic interactions (d) Van der Waals attractions

Aromatic carbon compounds such as benzene are planar and very stable. Double-bond character extends around the entire ring, which is why it is often drawn as a hexagon with a circle inside. This characteristic is caused by electron __________. (a) resonance. (b) pairing. (c) partial charge. (d) stacking.

Each nucleotide in DNA and RNA has an aromatic base. What is the principal force that keeps the bases in a polymer from interacting with water? (a) hydrophobic interactions (b) hydrogen bonds (c) covalent bonds (d) van der Waals interactions

Figure Q2-6 depicts the structure of carbon. Use the information in the diagram to choose the correct atomic number and atomic weight, respectively, for an atom of carbon. (a) 6, 12 (b) 12, 12 (c) 6, 18 (d) 12, 6

How do chromatin-remodeling complexes work? a. They use the energy from ATP hydrolysis to alter nucleosomes and make certain regions of the DNA more accessible to other proteins. b. They bind to nucleosomes in the 30-nm fiber and induce another level of packing, obscuring DNA from binding by other proteins c. They add methyl groups to the tails of histones in order to attract other proteins

Oligosaccharides are short sugar polymers that can become covalently linked to proteins and lipids through condensation reactions. These modified proteins and lipids are called glycoproteins and glycolipids, respectively. Within a protein, which of the amino acids (shown in Figure Q2-48) is the most probable target for this type of modification? Figure Q2-48 (a) serine (b) glycine (c) phenylalanine (d) methionine

The amino acids glutamine and glutamic acid are shown in Figure Q2-46. They differ only in the structure of their side chains (circled). At pH 7, glutamic acid can participate in molecular interactions that are not possible for glutamine. What types of interactions are these? Figure Q2-46 (a) ionic bonds (b) hydrogen bonds (c) van der Waals interactions (d) covalent bonds

The classic "beads-on-a-string" structure is the most decondensed chromatin structure possible and is produced experimentally. Which chromatin components are not retained when this structure is generated? a. linker histones b. linker DNA c. nucleosome core particles d. core histones

The images of chromosomes we typically see are isolated from mitotic cells. These mitotic chromosomes are in the most highly condensed form. Interphase cells contain chromosomes that are less densely packed and __________________________. a. occupy discrete territories in the nucleus b. share the same nuclear territory as their homolog c. are restricted to the nucleolus d. are completely tangled with other chromosomes

The structure that allows each duplicated eucaryotic chromosome to be pulled into a daughter cell is called a: a. centromere b. telomere c. mitotic spindle d. histone

There are 20100 different possible sequence combinations for a protein chain with 100 amino acids. In addition to the amino acid sequence of the protein, what other factors increase the potential for diversity in these macromolecules? (a) free rotation around single bonds during synthesis (b) noncovalent interactions sampled as protein folds (c) the directionality of amino acids being added (d) the planar nature of the peptide bond

What histone protein (considered a "linker" histone) is thought to pull nucleosomes together into a regular repeating array, resulting in a 30-nm fiber? a. histone H1 b. histone H2A c. histone H2B d. histone H3 e. histone H4

Which of the following expressions accurately describes the calculation of pH? (a) pH = -log10[H+] (b) pH = log10[H+] (c) pH = -log2[H+] (d) pH = -log10[OH-]

Which of the following factors do not influence the length of a covalent bond? (a) the tendency of atoms to fill the outer electron shells (b) the attractive forces between negatively charged electrons and positively charged nuclei (c) the repulsive forces between the positively charged nuclei (d) the minimization of repulsive forces between the two nuclei by the cloud of shared electrons

Which statement is true about the tight association of histone proteins and DNA? a. Histone proteins have a high proportion of positively charged amino acids, which attract the negatively charged phosphate groups on DNA. b. Histone proteins have deep grooves into which a DNA double helix tightly fits.

Which subatomic particles contribute to the atomic number for any given element? (a) protons (b) protons and neutrons (c) neutrons (d) protons and electrons

mitotic chromosomes are _____ times more compact than a DNA molecule in its extended form a. 10,000 b. 100,000 c. 1000 d. 100

the DNA from two different species can often be distinguished by a difference in the _______________. a. ratio of A + T to G + C b. ratio of A + G to C + T c. ratio of sugar to phosphate d. presence of bases other than A, G, C, and T

the polarity in a DNA strand is indicated by referring to one end as the 3' end and the other as 5' end. Which structure is on the 3' end? a. hydroxyl group b. phosphate group c. nitrogenous base

what is the most highly condensed form of chromatin? a. heterochromatin b. 30 nm chromatin fibers c. eucrhomatin

which of the following in NOT true? a. a cell can temporarily decondense its chromatin to silence genes during differentiation b. a cell can temporarily decondense its chromatin to give proteins rapid, localized access to specific DNA sequences c. a cell can grow temporarily decondense its chromatin to allow access to specific DNA sequences for replication, repair, or gene expression

fully folded proteins typically have polar side chains on their surfaces, where electrostatic attractions and hydrogen bonds can form between the polar group on the amino acid and the polar molecules in the solvent. in contrast, some proteins have a polar side chain in their hydrophobic interior. Which of the following could NOT occur to help accomodate an internal, polar side chain?

a hydrogen bond form polar and nonpolar side chains

protein structures have several different levels of organization. the primary structure of a protein is its amino acid sequence. the secondary and tertiary structures are more complicated. consider the definitions below and select the one that best fits the term "protein domain" a. the tertiary structure of a substrate-binding pocket b. a small cluster of a helices and B sheets c. a protein segment that folds dependently d. a segment of a polypeptide chain that can fold independently into a compact, stable structure

a segment of a polypeptide chain that can fold independently into a compact, stable structure

what is a protein family?

a structurally related group of proteins. (FEEDBACK: A protein family is a set of proteins that have similar primary structures (amino acid sequences) and thus have related three-dimensional structures. If the structure of one member of a protein family is determined, it can be used to make predictions about the structure of other members of the protein family.)

The homeobox codes for a protein domain that binds DNA. The homeobox is found in

a variety of genes that code for transcriptional regulators

Which of the following mechanisms describes how eukaryotic activator proteins can enhance transcription? (choose all correct answers, no partial credit)

a. binding to enhancer regions to promote formation of the transcription imitation complex b. recruiting chromatin-remodeling complexes to eject or slide nearby nucleosomes

Which of the following specialized DNA sequences provides an attachment point for the segregation of duplicated chromosomes? a. centromeres b. replication origins c. nucleosomes d. telomeres

a. centromeres

Nirenberg and Matthaei definitively showed that polyuridylic acid codes for polyphenyalanine because they were able to

a. make synthetic copies of the acid b. establish a cell-free system of translation c. use high-speed centrifugation to isolate macromolecules

Fatty acids can be used to produce energy by conversion to ___________ in the ___________ of the cell.

acetyl CoA; mitochondria

Which method is used for separating proteins based on specific interactions with other molecules?

affinity chromatography (FEEDBACK: Affinity chromatography separates proteins from one another by using a known molecular interaction with the protein of interest. Gel electrophoresis and mass spectrometry separate protein fragments by size and charge. X-ray crystallography is a method for determining the three-dimensional structure of a protein; it is not used for separation.)

the octameric histone core is composed of four different histone proteins, assembled in a stepwise manner. once the core octamer has been formed, DNA wraps around it to form a nucleosome core particle. Which of the following histone proteins forms part of the octameric core? a. H2A b. H3 C. H4 d. all of the above

all of the above

How does binding of GTP and GTP-binding protein affect this activity?

always activates the protein. (FEEDBACK: Proteins in the GTP-binding protein family are always in their active conformation when GTP is bound, in contrast to phosphorylation of a protein, which can activate or inactivate a protein. The hydrolysis of GTP to GDP returns the protein to the inactive state.)

How does tRNA become attached to the correct amino acid?

aminoacyl-tRNA synthetase

How do tRNAs become attached to the correct amino acid?

aminoacyl-tRNA synthetases

Which of the following does not increase the stability of eukaryotic mRNAs?

an intron

Reactions that build larger molecules in the cell are called ___________; reactions that break down molecules into smaller ones are called ___________.

anabolic; catabolic

Where or when does RNA capping at the 5' end of the transcript take place?

as an RNA is being transcribed

A cell can pass certain types of chromatin structure to daughter cells during cell reproduction. What molecules are key to this type of inheritance? a. DNA molecules b. histone proteins c. RNA molecules

Because there are four different monomer building blocks that can be used to assemble RNA polymers, the number of possible sequence combinations that can be created for an RNA molecule made of 100 nucleotides is _______. (a) 1004 (b) 4100 (c) 4 × 100 (d) 100/4

Both DNA and RNA are synthesized by covalently linking a nucleoside triphosphate to the previous nucleotide, constantly adding to a growing chain. In the case of DNA, the new strand becomes part of a stable helix. The two strands are complementary in sequence and antiparallel in directionality. What is the principal force that holds these two strands together? (a) ionic interactions (b) hydrogen bonds (c) covalent bonds (d) van der Waals interactions

Carbon 14 is an unstable isotope of carbon that decays very slowly. Compared to the common, stable carbon 12 isotope, carbon 14 has two additional ______________. (a) electrons. (b) neutrons. (c) protons. (d) ions.

DNA and RNA are different types of nucleic acid polymer. Which of the following is true of DNA but not true of RNA? (a) It contains uracil. (b) It contains thymine. (c) It is single-stranded. (d) It has 5′-to-3′ directionality.

Histone proteins pack DNA into a repeating array of DNA-protein particles called: a. heterochromatin b. nucleosomes c. euchromatin d. nucleoli

Interphase chromosomes are about______ times less compact than mitotic chromosomes, but still are about______ times more compact than a DNA molecule in its extended form. a. 10; 1000 b. 20; 500 c. 5; 2000 d. 50; 200

Table Q2-20 indicates the electrons in the first four atomic electron shells for selected elements. On the basis of the information in the chart and what you know about atomic structure, which elements are chemically inert? (a) carbon, sulfur (b) helium, neon (c) sodium, potassium (d) magnesium, calcium

The DNA in eucaryotic chromosomes is folded into a compact form by interactions with: a. RNA b. proteins c. euchromatin d. microtubules e. centromeres

The N-terminal tail of histone H3 can be extensively modified, and depending on the number, location, and combination of these modifications, these changes may promote the formation of heterochromatin. What is the result of heterochromatin formation? a. increase in gene expression b. gene splicing c. recruitment of remodeling complexes d. displacement of histone H1

The first task you are assigned in your summer laboratory job is to prepare a concentrated NaOH stock solution. The molecular weight of NaOH is 40. How many grams of solid NaOH will you need to weigh out to obtain a 500 mL solution that has a concentration of 10 M? (a) 800 g (b) 200 g (c) 400 g (d) 160 g

The human genome contains approximately how many genes? a. 500 b. 25,000 c. 100,000 d. 3,000,000,000

The structures that cap the ends of eucaryotic chromosomes are called: a. centromeres b. telomeres c. mitotic spindles d. histones

The variety and arrangement of chemical groups on monomer subunits contribute to the conformation, reactivity, and surface of the macromolecule into which they become incorporated. What type of chemical group is circled on the nucleotide shown in Figure Q2-45? Figure Q2-45 (a) pyrophosphate (b) phosphoryl (c) carbonyl (d) carboxyl

What evidence suggests that the large amount of excess "junk" DNA in a genome may serve an important function? a. all organisms have excess "junk" DNA b. A portion of "junk" DNA is highly conserved in its DNA sequence among many different eukaryotic species.

What structure in an interphase cell contains ribosomal RNA and proteins for the formation of ribosomes? a. chromatin b. nucleolus c. nuclear lamina

Which combination of answers best completes the following statement: When atoms are held together by ___________ __________, they are typically referred to as _________. (a) hydrogen bonds, molecules. (b) ionic interactions, salts. (c) ionic interactions, molecules. (d) double bonds, nonpolar.

Which of the following monomer building blocks is necessary to assemble selectively permeable boundaries around and inside cells? (a) sugars (b) fatty acids (c) amino acids (d) nucleotides

Which subatomic particles contribute to the atomic mass for any given element? (a) protons (b) protons and neutrons (c) neutrons (d) protons and electrons

the human genome comprises 23 pairs of chromosomes found in nearly every cell in the body. How many centromeres are in each cell? a. 23 b. 46 c. 69 d. 92 e. >200

the manner in which a gene sequence is related to its respective protein sequence is referred to as the ________ code. a. protein b. genetic c. translational d. expression

Heterochromatin can spread along a chromosome until it encounters a

barrier DNA sequence

The consistent diameter of the DNA double helix arises because of which property?

base pairing of pyrimidines with purines

The consistent diameter of the DNA double helix arises between of which property?

base pairing of pyrimidines with purines

Why is CO2 an end product of cellular respiration?

because it is the most stable form of carbon in our atmosphere

Why is sunlight the ultimate source of energy for nearly all living things on Earth?

because photosynthetic organisms produce food molecules using light energy

Why is the presence of oxygen required for the citric acid cycle to operate?

because the NADH passes its electrons to oxygen in the electron transport chain to renew NAD+

Tetracycline is an antibiotic that inhibits bacterial protein synthesis by

blocking the binding of aminoacyl-tRNA to the A site of the ribosome

At which step of gene expression can cells amplify the number of copies of a protein made form a single gene?

both transcription and translation

At which step of gene expression can cells amplify the number of copies of a protein made from a single gene?

both transcription and translation

Although the chromatin structure of interphase and mitotic chromosomes is very compact, DNA-binding proteins and protein complexes must be able to gain access to the DNA molecule. Chromatin-remodeling complexes provide this access by __________________. a. recruiting other enzymes b. modifying the N-terminal tails of core histones c. using the energy of ATP hydrolysis to move nucleosomes d. denaturing the DNA by interfering with hydrogen-bonding between base pairs

Double covalent bonds are both shorter and stronger than single covalent bonds, but they also limit the geometry of the molecule because they ____________________. (a) create a new arrangement of electron shells. (b) change the reactivity of the bonded atoms. (c) limit the rotation of the bonded atoms. (d) prevent additional bonds from being formed with the bonded atoms.

If the isotope 32S has 16 protons and 16 neutrons, how many protons, neutrons, and electrons will the isotope 35S have, respectively? (a) 16, 20, 15 (b) 16, 19, 15 (c) 16, 19, 16 (d) 16, 19, 17

Nucleosomes are formed when DNA wraps _____ times around the histone octamer in a ______ coil. a. 2.0; right-handed b. 2.5; left handed c. 1.7; left handed d. 1.3; right handed

Table Q2-21 indicates the electrons in the first four atomic electron shells for selected elements. On the basis of the information in the chart and what you know about atomic structure, which elements will form ions with a net charge of +1 in solution? (a) carbon, sulfur (b) helium, neon (c) sodium, potassium (d) magnesium, calcium

The core histones are small, basic proteins that have a globular domain at the C-terminus and a long extended conformation at the N-terminus. Which of the following is not true of the N terminal "tail" of these histones? a. it is subject to covalent modifications b. it extends out of the nucleosome core c. it binds to DNA in a sequence-specific manner d. it helps DNA pack tightly

The process of sorting human chromosomes pairs by size and morphology is called karyotyping. A modern method employed for karyotyping is called chromosome painting. How are individual chromosomes "painted"? a. with a laser b. using fluorescent antibodies c. using fluorescent DNA molecules d. using green fluorescent protein

What form of inheritance describes how a cell passes down chromatin structure (i.e., heterochromatin or euchromatin) from parent to daughter cells? a. genetic inheritance b. perigenetic inheritance c. epigenetic inheritance d. filial inheritance

Which subatomic particles can vary between isotopes of the same element, without changing the observed chemical properties? (a) electrons (b) protons and neutrons (c) neutrons (d) neutrons and electrons

what statement about nucleosomes is false? a. a nucleosome is a "bead" on a strong of unfolded chromatin b. a nucleosome produces a 3-fold packing ratio of DNA c. nucleosomes are found only in mitotic chromosomes d. a nucleosome consists of DNA wrapped around 8 histone proteins, plus a short segment of linker DNA

what type of bond connects base pairs? a. covalent bond b. ionic bond c. hydrogen bond

Which of the following is true about "junk DNA" a.It usually codes for proteins but the proteins are nonfunctional in the cell. b.It serves no biological function and is all just a remnant from evolution. c.Portions of junk sequence are conserved between species and thus may be functional. d. It is found at the ends of chromosomes from over replication during each cell cycle.

c. portions of junk sequence are conserved between species and thus may be functional

which of the following specialized DNA sequences provides an attachment point for the segregation of duplicated chromosomes?

centromeres

chlorophyll

Many transcriptional regulators function together to decide the expression level of a particular gene. This describes the concept of

combinatorial control

The presence of 5-methylcytosine within GC-rich regions of a gene's promoter is associated with

compacted chromatin

The structural feature of DNA that hints at the mechanism for its replication is the

complementary base pairing

The structure feature of DNA that hints at the mechanism for its replication is the

complementary base pairing

Disulfide bonds stabilize protein shape outside the cell by?

covalent bonds between cysteines. (FEEDBACK: Using mechanisms such as noncovalent bonds between charged side chains, proteins fold into their final conformation based on their amino acid sequence inside the cell. However, in the harsh environment outside the cell, this structure needs to be stabilized to keep its final form and function. Disulfide bonds are covalent cross-linkages between cysteine groups juxtaposed in the three-dimensional structure, and they act to hold the shape of the protein.)

which method is the most suitable for determining the three-dimensional structure of an extremely large integral membrane protein complex?

cryoelection microscopy (FEEDBACK: Large proteins produce confounding signals on NMR spectra, and large integral membrane complexes are hard to crystallize for x-ray crystallography. Structural studies of large integral membrane protein complex could be performed with cryoelectron microscopy. In this method, the purified protein complex is embedded in ice and a beam of electrons is used to collect projected images in multiple orientations.)

the most common covalent cross-links in proteins are sulfur-sulfur bonds that form between the amino acids with -SH (thiol) groups as side chains. Which amino acid has this side chain? a. phenylalanine b. lysine c. cysteine d. valine

cysteine

An ionic bond between two atoms is formed as a result of the ______________. (a) sharing of electrons. (b) loss of electrons from both atoms. (c) loss of a proton from one atom. (d) transfer of electrons from one atom to the other.

Avogadro's number, calculated from the atomic weight of hydrogen, tells us how many atoms or molecules are in a mole. The resulting base for all calculations of moles and molarity (how many molecules are present when you weigh out a substance or measure from a stock solution) is the following: 1 g of hydrogen atoms = 6 × 1023 hydrogen atoms = 1 mole of hydrogen Sulfur has a molecular weight of 32. How many moles and atoms are there in 120 grams of sulfur? (a) 3.75 and 6 × 1023 (b) 32 and 6 × 1023 (c) 1.75 and 1.05 ×1024 (d) 3.75 and 2.25 × 1024

Cells require one particular monosaccharide as a starting material to synthesize nucleotide building blocks. Which of the monosaccharides below fills this important role? (a) glucose (b) fructose (c) ribulose (d) ribose

Choose the answer that best fits the following statement: Cholesterol is an essential component of biological membranes. Although it is much smaller than the typical phospholipids and glycolipids in the membrane, it is a(n) _________________ molecule, having both hydrophilic and hydrophobic regions. (a) polar (b) oxygen-containing (c) hydrophobic (d) amphipathic

Many types of cells have stores of lipids in their cytoplasm, usually seen as fat droplets. What is the lipid most commonly found in these droplets? (a) cholesterol (b) palmitic acid (c) isoprene (d) triacylglycerol

Polar covalent bonds are formed when the electrons in the bond are not shared equally between the two nuclei. Which one of these molecules contains polar bonds? (a) molecular oxygen (b) methane (c) propane (d) water

Table Q2-22 indicates the electrons in the first four atomic electron shells for selected elements. On the basis of the information in the chart and what you know about atomic structure, which elements will form ions with a net charge of +2 in solution? (a) carbon, sulfur (b) helium, neon (c) sodium, potassium (d) magnesium, calcium

The complex of DNA and protein in chromosomes is called: a. centromeres b. histone c. centrosome d. chromatin

The human genome comprises 23 pairs of chromosomes found in nearly every cell in the body. How many telomeres are in each cell? a. 23 b. 46 c. 69 d. 92 e. >200

The human genome has enough DNA to stretch more than 2 m. However, this DNA is not contained in a single molecule; it is divided into linear segments and packaged into structures called chromosomes. What is the total number of chromosomes found in each of the somatic cells in your body? a. 22 b. 23 c. 44 d. 46

The octameric histone core is composed of four different histone proteins, assembled in a stepwise manner. Once the core octamer has been formed, DNA wraps around it to form a nucleosome core particle. Which of the following histone proteins does not form part of the octameric core? a. H4 b. H2A c. H3 d. H1

The pH of an aqueous solution is an indication of the concentration of available protons. However, you should not expect to find lone protons in solution; rather, the proton is added to a water molecule to form a(n) ______________ ion. (a) hydroxide (b) ammonium (c) chloride (d) hydronium

Which of the following chemical groups is not used to construct a DNA molecule? a. 5-Carbon sugar b. phosphate c. Nitrogen-containing base d. 6-carbon sugar

Which of the following is true for most genes? a. A gene is a segment of DNA that contains the instructions for making a particular protein b. A gene is a segment of DNA that contains the instructions for making a particular RNA c. A gene is a region of DNA that controls a discrete hereditary characteristic of an organism d. all of the above

You have a concentrated stock solution of 10 M NaOH and want to use it to produce a 150 mL solution of 3 M NaOH. What volume of water and stock solutions will you measure out to make this new solution? (a) 135 mL of water, 15 mL of NaOH stock (b) 115 mL of water, 35 mL of NaOH stock (c) 100 mL of water, 50 mL of NaOH stock (d) 105 mL of water, 45 mL of NaOH stock

the core histone proteins have tails that can be chemically modified by what type of group? a. acetyl b. phosphate c. methyl d. any of the above

If a reaction is energetically favorable (exergonic), then it must produce a(n)

decrease in reaction time.

Researchers assayed the activity of enzyme F in three different types of tissue from the same mouse by determining the amount of enzyme product produced per milligram of tissue per unit time. As shown in the graph below, results indicate more product generation in the liver compared to the kidney and muscle samples. Which of the following factors might explain the different results among the three tissues?

differences in the post-translational modifications of the enzyme among the tissue types differences in the transcription of the gene encoding the enzyme among the tissue types differences in the translation of the mRNA encoding the protein among the tissue types

What purpose does NADPH serve in biosynthetic reactions like the one pictured below?

donating electrons for a reduction reaction

When are chromosomes in their most compacted form?

during mitosis

The human genome comprises 23 pairs of chromosomes found in nearly every cell in the body. How many replication origins are in each cell? a. 23 b. 46 c. 69 d. 92 e. >200

DNA replication is considered semiconservative because__________. a. after many rounds of DNA replication, the original DNA double helix is still intact b. each daughter DNA molecule consists of one strand from the parent DNA molecule and one new strand c. each daughter DNA molecule consists of two new strands copied from the parent DNA molecule d. new DNA strands must be copied from a DNA template

each daughter DNA molecule consists of one strand from the parent DNA molecule and one new strand

What is the role of oxygen in the electron transport chain?

electron acceptor

What type of bonds are formed between histone proteins and DNA to form nucleosome core particles?

electrostatic interactions

Comparing the relative number of chromosome pairs is a good way to determine whether two species are closely related. true/false

false

DNA molecules, like proteins, consist of a single, long polymeric chain that is assembled from small monomeric subunits true/false

false

Determine whether the following statement is true or false: Different cell types that respond to the same hormone usually turn on the same sets of genes.

false

Determine whether the following statement is true or false: In the laboratory, transcription regulators can be used to convert one differentiated cell type into another cell type, but not to convert differentiated cells into a less differentiated, pluripotent stem cells.

false

Determine whether the following statement is true or false: Once a cell has become specialized to produce the set of proteins that are responsible for its distinctive properties, its gene expression patterns remain fixed.

false

Determine whether the following statement is true or false: The general transcription factors that assemble at a eukaryotic promoter are different, depending on the specific gene being transcribed by polymerase II.

false

Gene sequences correspond exactly to the respective protein sequences produced from them. true/false

false

Hydrogen bonds between each nucleotide hold individual DNA strands together true/false

false

In the chromatin of interphase chromosomes, regions of the chromosome that contain genes being expressed are generally more compact, while those that contain quiescent genes are more generally more extended. true/false

false

The telomere is a specialized DNA sequence where microtubules from the mitotic spindle attach to the chromosome so that duplicate copies move to opposite ends of the dividing cell. true/false

false

The first living things on Earth probably generated ATP by what mechanism?

fermentation

Using powerful new sequencing technologies, investigators can now catalog every RNA molecule made by a cell and determine at what quantities these RNAs are present. In an experiment, researchers measured the relative quantities of two different mRNAs—one transcribed from gene A, the other from gene B—in two different cell types. Gene B is expressed in both the liver and the brain whereas gene A is expressed in the brain but not in the liver. Which most likely encodes a housekeeping protein?

gene B only

In eukaryotes, what must assemble at a promoter before RNA polymerase can transcribe a gene?

general transcription factors

If lactose and glucose are both available to a bacterial cell, which carbon sources will be used?

glucose

The food molecule whose breakdown generates most of the energy for a majority of animal cells is

glucose

Glycogen synthetase enzyme, which forms glycogen from glucose, is activated by excess

glucose 6-phosphate

The energies of phosphate bonds for different molecules in glycolysis are shown. Based on this graphic, the transfer of a phosphate from which of the molecules to ADP (to form ATP) is energetically UNFAVORABLE?

glucose 6-phosphate

Individuals with inherited diseases causing mitochondrial dysfunction typically experience which of the following symptoms?

heart problems

Living systems can generate and maintain order without violating the second law of thermodynamics because they generate

heat

Hypoacetylated histone tails are usually associated with... (choose all correct answers)

heterochromatin genes with low levels of expression

Biochemical subcompartments that form inside the nucleus are distinct from their immediate surroundings because of the?

high concentrations of interacting proteins and RNA. (FEEDBACK: Biochemical subcompartments can form inside of organelles by the aggregation of interacting proteins, RNA, and protein complexes that perform a concerted function. These "intracellular condensates" are simply concentrations of molecules; they are not bound by a membrane, nor are they hydrophobic droplets.)

although all protein structures are unique, there are common structural building blocks that are referred to as regular secondary structures. some proteins have a helices , some have B sheets, and still others have a combination of both. what makes it possible for proteins to have these common structural elements? a. specific amino acid sequences b. side-chain interactions c. the hydrophobic-core interactions d. hydrogen bonds along the protein backbone

hydrogen bonds along the protein backbone

two or three a helices can sometimes wrap around each other to form coiled-coils. the stable wrapping of one helix around another is typically driven by ________ interactions. a. hydrophilic b. hydrophobic c. van der Waals d. ionic

hydrophobic

If one end of a DNA strand has a phosphate group on it, the chemical group on the other end must be

hydroxyl

Where does the splicing of pre-mRNAs take place?

in the nucleus as the RNA is still being transcribed

When a ligand binds to an allosteric enzyme's regulatory site, it changes the activity of that enzyme by?

inducing a conformational change. ( Once a regulatory molecule or ligand binds to a regulatory site, an allosteric protein undergoes a conformational change that is transmitted to the active site. Inducing the conformational change can change the activity of the enzyme, but it does NOT directly block the active site.)

proteins bind selectively to small-molecule targets called ligands. the selection of one ligand out of a mixture of possible ligands depends on the number of weak, noncovalent interactions in the protein's ligand-binding site. where is the binding site typically located in the protein structure? a. on the surface of the protein b. inside a cavity on the protein surface c. buried in the interior of the protein d. forms on the surface of the protein in the presence of ligand

inside a cavity on the protein surface

Protons are pumped across the mitochondrial inner membrane to accumulate in the

intermembrane space

In eukaryotes, which parts of a gene are transcribed into RNA?

introns and exons

How does methylation of histone tails affect the accessibility of DNA?

it can have different effects depending on the location

which of the following is a function of the protein component of chromosomes?

it packages the DNA strands

adds phosphate groups to molecules

kinase

What is the fermentation product produced in an anaerobic muscle cell?

lactic acid

The catalytic sites for peptide bond formation during translation is found in which part of the ribosome?

large subunit RNAs

later in the chain

joins two ends of DNA together

ligase

The reading frame to use for translating am mRNA into functional protein is determined by the

location of an AUG

The reading frame to use for translating an mRNA into functional protein is determined by the

location of an AUG.

In the cell, enhancer sequence functions are limited in their range of action by the formation of ___________ that hold specific genes and enhancers in close proximity.

loops

Enzymes increase the speed of a chemical reaction because they

lower the activation energy needed to start the reaction.

Which type of RNA is converted into protein for performing its cellular function?

mRNA

MicroRNAs block the expression of a specific gene product by binding to the ___________ and inhibiting ___________.

mRNA; translation

which of the following diseases result from protein misfolding? a. mad cow disease b. happy cow disease c. indifferent cow disease d. anxious cow disease

mad cow disease

A binding site on the surface of a protein interacts specifically with another protein through?

many weak noncovalent interactions. (FEEDBACK: Covalent interactions are rarely used between protein molecules because they are difficult to break, often requiring an enzyme. Interactions between proteins and their partners need to be reversible but very specific. A specific interaction, but one that is able to be altered, can be achieved through formation of many weak noncovalent interactions between proteins and their binding partners.)

The proton flow through the transmembrane H+ carrier of ATP synthase results in

mechanical rotation that is converted into the chemical-bond energy of ATP.

In eukaryotes, the initiator tRNA always carries which amino acid?

methionine

If the products of a reaction have more free energy than the reactants, then that reaction is

not energetically favorable.

What structure is responsible for selecting and transporting only properly processed eukaryotic mRNAs into the cytoplasm?

nuclear pore complex

hydrolyzes bonds between nucleotides

nuclease

Pre-mRNAs must be capped, polyadenylated, and spliced in the _____________ before they can be _________________.

nucleus; exported

How many different aminoacyl-tRNA synthetases do most organisms have?

one for each amino acid

which of the following is a feature commonly observed in B sheets? a. anti-paradoxical regions b. coiled-coil patterns c. shortened polypeptide backbone d. parallel regions

parallel regions

removes a phosphate group from a molecule

phosphatase

RNA polymerases join nucleotides through what kind of bond?

phosphodiester

The type of bond that holds together neighboring subunits in a single strand of DNA is a

phosphodiester bond

The first step of glycolysis uses one ATP molecule in order to

phosphorylate glucose

Which of the following correctly matches the cellular location with the production of ATP by oxidative phosphorylation in that cell type?

plasma membrane—bacteria

Eukaryotic repressor proteins can decrease transcription using which of the following mechanisms?

preventing the assembly of the transcription initiation complex

Cellular respiration ___________ energy and produces ___________, whereas photosynthesis ___________ energy and produces ___________.

produces; water + carbon dioxide; consumes; oxygen + sugars

which regulatory element does the RNA polymerase bind to?

promoter

To begin transcription, eukaryotic RNA polymerase recognizes nucleotide sequences in what region of the DNA?

promoter region

What is the name of the complex that degrades proteins that have reached the end of their lifespan, are damaged, or are misfolded?

proteasome

Some mRNAs from the bacterium Listeria monocytogenes contain a "thermosensor" sequence that can regulate _________________ in a temperature-dependent manner.

protein translation

How is pyruvate imported into the mitochondrial matrix for use in the citric acid cycle?

proton gradient-driven symport

Which of the following mechanisms describes how eukaryotic activator proteins can regulate chromatin packaging to enhance transcription?

recruiting chromatin-remodeling complexes to eject or slide nearby nucleosomes

In an enzymatic reaction, a molecule gains an electron. This is known as a(n) ___________ reaction.

reduction

Chlorophyll appears green because it

reflects green light

What recognizes the stop codons in an mRNA?

release factor

the structure of a folded protein is determined by x-ray crystallography. what model best displats a protein's secondary structures (a helices and B sheets)? a. ribbon/cartoon b. space-filling c. backbone d. wire

ribbon/cartoon

It has been proposed that the first cells used RNA for both information storage and catalysis and that DNA and proteins evolved later. Which modern macromolecules may be relics of the hypothesized RNA world?

ribosome spliceosome

An RNA message is decoded by which of the following?

ribosomes

What is the best term for an RNA molecule that possesses catalytic activity?

ribozyme

Long noncoding RNA (lncRNA) can function as a(n)

scaffold for proteins

a leucine zipper is composed of two dimerized alpha helices. hydrogen bonding within each alpha helix is an example of which of the following? a. primary structure b. quarternary structure c. tertiary structure d. secondary structure

secondary structure

which of the three models for DNA replication was supported by Meselson and Stahl when DNA isolated from bacteria that had first been grown in heavy 15N media then transferred to light 14N media gave an intermediate band as show on the right? a. dispersive b. semiconservative c. conservative

semiconservative

What are two types of noncoding regulatory RNAs?

siRNAs and miRNAs

What is the name of the subunit of bacterial RNA polymerase that recognizes the promoter of a gene?

sigma factor

Gluconeogenesis requires a total of ___________ ATP and GTP molecules combined.

six

DNA polymerases are processive, which means that they remain tightly asssociated with the template strand while moving rapidly and adding nucleotides to the growing daughter strand. which piece of the replication machinery accounts for this characteristic? a. helicase b. sliding clamp c. single-strand binding protein d. primase

sliding clamp

Refer to the diagram below. If cells that cannot carry out fermentation were grown in anaerobic conditions, at which step would glycolysis halt?

step 6: where NAD+ is converted to NADH

In addition to being converted to acetyl CoA for the citric acid cycle, pyruvate made during glycolysis can be used for

synthesis of alanine and fermentation.

which of the following is found only in eukaryotic genomes, and NOT in prokaryotic genomes?

telomeres

The low redox potential of NADH means that it has a

tendency to give up electrons

At which site on the DNA of a gene does RNA polymerase release its newly made RNA

terminator

WHich of the following is true about amyloid protein structures?

thay consists of stacked B (beta) sheets (FEEDBACK: Amyloid protein structures are β sheets that interlock with each other through their side chains and form stacks. Since they are made from many β sheets, they form strong structures that have many roles in the cell, including formation of important cellular compartments. However, some amyloid structures, but not all, are abnormal and cause disease.)

To which part of an mRNA molecule do ribosomal subunits first bind?

the 5' end

Which part of a protein is synthesized by a ribosome first?

the N-terminus

The assembly of general transcription factors at a eukaryotic promoter typically begins at what site?

the TATA box

In eukaryotes, multiple genes can be expressed simultaneously by

the binding of a specific transcriptional regulator to several genes

The Michaelis constant (KM) of an enzyme is a measure of?

the binding strength of enzyme to substrate. ( FEEDBACK: Enzyme activity is measured using two values. The first is the rate at which the enzyme converts the substrate to product, which is called Vmax. This value is determined by measuring the rate of product formation in conditions where all enzyme binding sites are occupied by substrate. The Michaelis constant measures the relative binding strength of the enzyme to substrate, determined by the concentration of substrate at which the enzyme operates at half of its Vmax.)

DNA is a better molecule for long-term storage of genetic information than RNA because

the deoxyribose sugar stabilizes DNA chains

DNA is a better molecule for long term storage of genetic information that RNA because

the deoxyribose sugar stabilizes DNA chains.

Fred Griffith studied two strains of Streptococcus pneumonia, one that causes a lethal infection when injected into mice, and a second that is harmless. He observed that pathogenic bacteria that have been killed by heating can no longer cause an infection. But when these heat-killed bacteria are mixed with live, harmless bacteria, this mixture is capable of infecting and killing a mouse. What did Griffith conclude from this experiment? a. the infectious strain cannot be killed by heating b. the heat-killed pathogenic bacteria "transformed" the harmless strain into a lethal one c. the harmless strain somehow revived the heat-killed pathogenic bacteria d. the mice had lost their immunity to infection with S. pneumoniae

the heat-killed pathogenic bacteria "transformed" the harmless strain into a lethal one.

When Griffith injected heat-killed infections bacteria mixed with live harmless bacteria, he found that the mice died because

the live harmless bacteria were transformed into infectious bacteria

When Griffith injected heat-killed infectious bacteria mixed with live harmless bacteria, he found that the mice died because

the live harmless bacteria were transformed into infectious bacteria

Which would be more deleterious: the loss of a single nucleotide from the protein-coding region of a gene or the loss of three nucleotides in that same region?

the loss of a single nucleotide

The part of the DNA molecule that carries the information of producing protein is

the order of the nucleotide bases

What is gluconeogenesis?

the synthesis of glucose from pyruvate

GroEL/GroES is an example of a chaperone protein complex. Which of the following is NOT true of molecular chaperones? a. they assist polypeptide folding by helping the folding process follow the most energetically favorable pathway b. they can isolate proteins from other components of the cell until folding is complete c. they can interact with unfolded polypeptides in a way that changes the primary structure of the protein d. they help streamline the protein-folding process by making it a more efficient and reliable process inside the cell

they can interact with unfolded polypeptides in a way that changes the primary structure of the protein

the correct folding of proteins is necessary to maintain healthy cells and tissues. unfolded proteins are responsible for such neurodegenerative disorders as Alzeimer's disease, Huntington's disease, and Creutzfeldt - Jakob disease (the specific faulty protein is different for each disease). What is the ultimate fate of these disease-causing, unfolded proteins? a. they are degraded b. they bind a different target protein c. they form structured filaments d. they form protein aggregates

they form protein aggregates

how do changes in histone modifications lead to changes in chromatin structure? a. they directly lead to changes in the positions of the core histones b. they change the affinity between the histone octamer and the DNA c. they help recruit other proteins to the chromatin for remodeling d. they cause the histone N-terminal tails to become hyperextended

they help recruit other proteins to the chromatin for remodeling

Several organisms have a homologous protein (inherited from a common ancestor) that is highly similar at the amino acid level. You are comparing the genes that code for these proteins in the different organisms when you note that one of the codon nucleotide positions shows more nucleotide variation than the other nucleotide positions. In which codon nucleotide position do you expect to see the most variability among species?

third nucleotide position

molecular chaperones can work by creating an "isolation chamber". what is the purpose of this chamber? a. the chamber acts as a garbage disposal, degrading improperly folded proteins so that they do not interact with properly folded proteins b. this chamber is used to increase the local protein concentration, which will help speed up the folding process c. this chamber serves to transport unfolded proteins out of the cell d. this chamber serves to protect unfolded proteins from interacting with other proteins in the cytosol, until protein folding is completed.

this chamber serves to protect unfolded proteins from interacting with other proteins in the cytosol, until protein folding is completed.

How many nucleotides are necessary to specify a single amino acid?

three

In principle, how many reading frames in an RNA molecule can potentially be translated into protein?

three

The information in an mRNA molecule is converted into protein sequence using

three consecutive bases, with no overlap between triplets.

Shown is a chloroplast with labeled structures. The photosynthetic machinery is found in which of the compartments shown?

thylakoid membrane

What is the function of a kinase?

to add a phosphate group to a molecule

What is a function of the nucleolus?

to assemble ribosomal RNA and proteins into ribosomes

All of the RNA in a cell is made by what process?

transcription

The process of gene expression always involves which process(es) described in the central dogma?

transcription

Chromosomes exist at different levels of condensation, depending on the stage of the cell cycle. true/false

true

Determine whether the following statement is true or false: In bacteria, most protein-coding genes lack introns.

true

Each strand of DNA contains all the information needed to create a new double-stranded DNA molecule with the same sequence information. true/false

true

Eucaryotic chromosomes contain many different sites where DNA replication can be initiated. true/false

true

Histone tail modifications establish and maintain the different chromatin structures found in heterochromatin and euchromatin. true/false

true

The polarity of a DNA strand results from the polarity of the nucleotide subunits true/false

true

Excess amounts of the amino acid tryptophan result in downregulation of the expression of the enzymes required for its synthesis because

tryptophan binds to and activates the Trp repressor

THe function of feedback inhibition of an enzyme pathway is to?

turn off synthesis of a product when it is abundance. ( Feedback inhibition keeps the cell from accumulating unnecessarily large amounts of biological compounds by reversibly inhibiting an enzyme in the biosynthetic pathway for that compound. These mechanisms shut down the enzymes early in the pathway so that wasteful intermediates do not accumulate.)

During glycolysis, the number of ATP consumed (per glucose molecule) is ___________, while the number produced is ___________.

two; four

Glycolysis produces ___________ ATP molecules, whereas the complete oxidation of glucose to water and carbon dioxide produces ___________ ATP molecules.

two; thirty

Which of the following is a mobile electron carrier in the electron-transport chain?

ubiquinone

Condensation reactions are energetically ___________ and hydrolysis reactions are energetically ___________.

unfavorable; favorable

In eukaryotes, where do transcription regulators bind?

upstream, downstream, or within the genes they control

On its own, RNA polymerase binds _____________ to gene promoters that are regulated by transcriptional activators, but binds ______________ to promoters that are regulated with transcriptional repressors .

weakly; strongly

What is the value of ΔG at equilibrium?

zero

What is the relationship between ΔG and ΔG0?

ΔG0 is the free-energy change at standard temperature and concentrations.

Even though proteins can form channels across biological membranes using either α helices or β sheets, channels made of α helices are more versatile. Explain the physical constraints on β-barrel structures and why these constraints do not apply to channels made of α helices.

β-Barrel structures are composed of individual β strands that form a β sheet that needs to be curved to make the structure of a pore in the membrane. The physical constraints are due to very specific positioning of each strand to maintain the necessary hydrogen- bonding network within the sheet. The relative positions of α helices can vary and still form strong interactions with other helices in the transmembrane region of a protein.

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