BIOS 041-HW/Quiz Questions Ch1-7, 11-14, 16-17

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The final metabolite produced by glycolysis is ___________. Select one: a. glyceraldehyde 3-phosphate b. acetyl CoA c. 3-phosphoglycerate d. pyruvate

What part of the DNA replication process would be most directly affected if a strain of bacteria lacking DNA ligase were used to make the cell extracts? Select one: a. initiation of DNA synthesis b. Okazaki fragment synthesis c. leading-strand elongation d. lagging-strand completion

What part of the DNA replication process would be most directly affected if a strain of bacteria lacking the exonuclease activity of DNA polymerase were used to make the cell extracts? Select one: a. initiation of DNA synthesis b. Okazaki fragment synthesis c. leading-strand elongation d. lagging-strand completion

Which of the following DNA strands can form a DNA duplex by pairing with itself at each position? Select one: a. 5′-AAGCCGAA-3′ b. 5′-AAGCCGTT-3′ c. 5′-AAGCGCAA-3′ d. 5′-AAGCGCTT-3′

Which of the following events does not usually occur during interphase? Select one: a. The centrosomes are duplicated. b. DNA is replicated. c. Cells grow in size d. The nuclear envelope breaks down

Which of the following is not true of molecular chaperones? Select one: a. They help streamline the protein-folding process by making it a more efficient and reliable process inside the cell. b. They assist polypeptide folding by helping the folding process follow the most energetically favorable pathway. c. They can isolate proteins from other components of the cells until folding is complete. d. They can interact with unfolded polypeptides in a way that changes the final fold of the protein

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? Select one: a. Produce lipids with hydrocarbon tails that are longer and have fewer double bonds b. Decrease the amount of cholesterol in the membrane. c. Decrease the amount of glycolipids in the membrane. d. Produce lipids with hydrocarbon tails that are shorter and have more double bonds.

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? Select one: a. hydrophobic interactions b. Van der Waals attractions c. hydrogen bonds d. electrostatic attractions

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? Select one: a. van der Waals interactions b. covalent bonds c. ionic interactions d. hydrogen bonds

Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell. Which of the following ions is the most abundant outside a typical mammalian cell? Select one: a. Ca2+ b. Cl- c. K+ d. Na+

Diversity among the oligosaccharide chains found in the carbohydrate coating of the cell surface can be achieved in which of the following ways? Select one: 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

Even though DNA polymerase has a proofreading function, it still introduces errors in the newly synthesized strand at a rate of 1 per 107 nucleotides. To what degree does the mismatch repair system decrease the error rate arising from DNA replication? Select one: a. 2-fold b. 5-fold c. 10-fold d. 100-fold

Foods are broken down into simple molecular subunits for distribution and use throughout the body. Which type of simple subunits, listed below, is used preferentially as an energy source? Select one: a. glycerol b. free fatty acids c. proteins d. simple sugars

Both excitatory and inhibitory neurons form junctions with muscles. By what mechanism do inhibitory neurotransmitters prevent the postsynaptic cell from firing an action potential? Select one: a. by closing Na+ channels b. by preventing the secretion of excitatory neurotransmitters c. by opening K+ channels d. by opening Cl- channels

d; Inhibitory neurons release inhibitory neurotransmitters such as GABA and glycine. They bind to and open ligand-gated Cl- channels. If Na +channels are open, Cl- ions will rush into the cell as well, neutralizing the positive charges carried by Na+.

Similar to oxidative phosphorylation, the electrons passed along the chloroplast electron-transport chain are ultimately passed on to a molecule of O2, to produce H2O. Select one: True False

false

The electron-transport proteins, utilized in stage 1 of photosynthesis, reside in the inner membrane of the chloroplast. Select one: True False

false

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 would not occur to help accommodate an internal, polar side chain? Select one: a. Hydrogen bonds form between polar side chains and a buried water molecule. b. A hydrogen bond forms between two polar side chains. c. A hydrogen bond forms between a polar side chain and the protein backbone. d. A hydrogen bond forms between a polar side chain and an aromatic side chain.

How does the total number of replication origins in bacterial cells compare with the number of origins in human cells? Select one: a. 1 versus 100 b. 5 versus 500 c. 10 versus 1000 d. 1 versus 10,000

If the genome of the bacterium E. coli requires about 20 minutes to replicate itself, how can the genome of the fruit fly Drosophila be replicated in only 3 minutes? Select one: a. The Drosophila genome is smaller than the E. coli genome. b. Eukaryotic DNA polymerase synthesizes DNA at a much faster rate than prokaryotic DNA polymerase. c. The nuclear membrane keeps the Drosophila DNA concentrated in one place in the cell, which increases the rate of polymerization. d. Drosophila DNA contains more origins of replication than E. coli DNA.

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? Select one: a. glycosylases b. convertases c. phospholipases d. flippases

Pyruvate is an important metabolic intermediate that can be converted into several other compounds, depending on which enzyme is catalyzing the reaction. Which of the following cannot be produced from pyruvate in a single enzyme-catalyzed reaction? Select one: a. oxaloacetate b. alanine c. lactate d. citrate

Several different classes of enzymes are needed for the catabolism of carbohydrates. Which of the following descriptions best matches the function of a kinase? Select one: a. An enzyme that catalyzes the rearrangement of bonds within a single molecule. b. An enzyme that catalyzes a change in the position of a specific chemical group within a single molecule. c. An enzyme that catalyzes the oxidation of a molecule by removing a hydride ion. d. An enzyme that catalyzes the addition of phosphate groups to other molecules

Some cells have aquaporins — channels that facilitate the flow of water molecules through the plasma membrane. For these cells, what regulates the rate and direction of water diffusion across the membrane? Select one: a. availability of ATP b. aquaporin conformation c. resting membrane potential d. solute concentrations on either side of the membrane

Telomeres serve as caps at the ends of linear chromosomes. Which of the following is not true regarding the replication of telomeric sequences? Select one: a. The lagging-strand telomeres are not completely replicated by DNA polymerase. b. Telomeres are made of repeating sequences. c. Additional repeated sequences are added to the template strand. d. The leading strand doubles back on itself to form a primer for the lagging strand.

The ATP synthase found in chloroplasts is structurally similar to the ATP synthase in mitochondria. Given that ATP is being synthesized in the stroma, where will the F0 portion of the ATP synthase be located? Select one: a. inner membrane b. stroma c. thylakoid space d. thylakoid membrane

Transcription is similar to DNA replication in that ___________________. Select one: a. an RNA transcript is synthesized discontinuously and the pieces are then joined togethe b. it uses the same enzyme as that used to synthesize RNA primers during DNA replication. c. the newly synthesized RNA remains paired to the template DNA. d. nucleotide polymerization occurs only in the 5′-to-3′direction.

Unlike DNA, which typically forms a helical structure, different molecules of RNA can fold into a variety of three-dimensional shapes. This is largely because___________________. Select one: a. RNA contains uracil and uses ribose as the sugar. b. RNA bases cannot form hydrogen bonds with each other. c. RNA nucleotides use a different chemical linkage between nucleotides compared to DNA. d. RNA is single-stranded.

What color is reflected by (most) plants? Select one: a. Red b. White c. Black d. Green

Which of the following methods is not used by cells to regulate the amount of a protein in the cell? Select one: a. Genes can be transcribed into mRNA with different efficiencies. b. Many ribosomes can bind to a single mRNA molecule. c. Proteins can be tagged with ubiquitin, marking them for degradation d. Nuclear pore complexes can regulate the speed at which newly synthesized proteins are exported from the nucleus into the cytoplasm.

Which of the following questions would not be answered by using karyotyping? Select one: a. Is the individual genetically female or male? b. Do any of the chromosomes contain pieces that belong to other chromosomes? c. Does the individual have an extra chromosome? d. Do any chromosomes contain point mutations?

Which of the following statements correctly explains what it means for DNA replication to be bidirectional? Select one: a. The replication fork can open or close, depending on the conditions . b. The DNA replication machinery can move in either direction on the template strand. c. Replication-fork movement can switch directions when the fork converges on another replication fork. d. The replication forks formed at the origin move in opposite directions.

Which three amphipathic lipids are present in the cell membrane? Select one: a. Sphingomyelin, Sterols, Flippases b. Phospholipids, hydrolipids, gylcosylated lipids c. Phosopholipids, transmembrane receptors, sterols d. Phospholipids, glycolipids, sterols

You are studying a disease that is caused by a virus, but when you purify the virus particles and analyze them you find they contain no trace of DNA. Which of the following molecules are likely to contain the genetic information of the virus? Select one: a. high-energy phosphate groups b. carbohydrates c. lipids d. RNA

snRNAs ___________________. Select one: a. are translated into snRNPs. b. are important for producing mature mRNA transcripts in bacteria. c. are removed by the spliceosome during RNA splicing. d. can bind to specific sequences at intron-exon boundaries through complementary base-pairing.

ΔG measures the change of free energy in a system as it converts reactant (Y) into product (X). When [Y] =[X], ΔG is equal to _____________. Select one: a. ΔG° + RT b. RT c. ln [X]/[Y] d. ΔG°

Which of the following molecules is thought to have arisen first during evolution? Select one: a. all came to be at the same time b. protein c. DNA d. RNA

d; Because RNA is known to catalyze reactions within the cell, because the components of RNA are thought to be more readily formed in the conditions on primitive Earth, and because RNA can contain genetic information, it is the most likely of the three molecules to have arisen first in evolution

Which of the following occur without coupling transport of the solute to the movement of a second solute? Select one: a. import of glucose into gut epithelial cells b. the export of Na+ from cells to maintain resting membrane potential c. export of H+ from animal cells for pH regulation d. export of Ca2+ from the cytosol

d; Ca2+ is exported using ATP-powered pumps. There are no other solutes that are being moved by these pumps.

Which of the following statements about the proteasome is false? Select one: a. The protein stoppers that surround the central cylinder of the proteasome use the energy from ATP hydrolysis to move proteins into the proteasome inner chamber. b. Proteases reside in the central cylinder of a proteasome. c. Ubiquitin is a small protein that is covalently attached to proteins to mark them for delivery to the proteasome. d. Misfolded proteins are delivered to the proteasome, where they are sequestered from the cytoplasm and can attempt to refold.

d; Once proteins are sent to the proteasome, proteases degrade them. Chaperone proteins provide a place for misfolded proteins to attempt to refold.

What do you predict would happen if you created a tRNA with an anticodon of 5′-CAA-3′ that is charged with methionine, and added this modified tRNA to a cell-free translation system that has all the normal components required for translating RNAs? Select one: a. translation would no longer be able to initiate b. methionine would be incorporated into proteins at some positions where valine should be c. methionine would be incorporated into proteins at some positions where glutamine should be d. methionine would be incorporated into proteins at some positions where leucine should be

d; The 5′-CAA-3′anticodon binds to the 5′-UUG-3′codon, which normally codes for leucine.

Which of the following statements is true? Select one: a. Bacteria and animal cells rely on the Na+-K+ pump in the plasma membrane to prevent lysis resulting from osmotic imbalances. b. Amoebae have transporter proteins that actively pump water molecules from the cytoplasm to the cell exterior. c. The Na+-K+ pump allows animal cells to thrive under conditions of very low ionic strength. d. The Na+-K+ pump helps to keep both Na+ and Cl- ions out of the cell.

d; The Na+-K+ pump keeps Na+ out directly by pumping it out and keeps Cl- out indirectly by helping to maintain the negative membrane potential.

Each round of the Calvin cycle uses five molecules of CO2 to produce one molecule of glyceraldehyde 3-phosphate and one of pyruvate. Select one: True False

false

Indicate whether the following statements are true or false. 2. Phosphatidylserine is the most abundant type of phospholipid found in cell membranes ____ ______.

false

Indicate whether the following statements are true or false. 4. The highly ordered structure of the lipid bilayer makes its generation and maintenance energetically unfavorable ________.

false

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. Interphase chromosomes contain both darkly staining _______________ and more lightly staining ________________. Genes that are being transcribed are thought to be packaged in a ________________ condensed type of euchromatin. Nucleosome core particles are separated from each other by stretches of _______________ DNA. A string of nucleosomes coils up with the help of _______________ to form the more compact structure of the _______________. A ________________ model describes the structure of the 30-nm fiber. The 30 nm chromatin fiber is further compacted by the formation of _______________ that emanate from a central ________________.

heterochromatin, euchromatin, less, linker, histone H1, 30-nm fiber, zigzag, loops, axis

An electron bound to a molecule with low affinity for electrons is a _______-energy electron. Transfer of an electron from a molecule with low affinity to one with higher affinity has a __________ ΔG° and is thus ____________ under standard conditions. If the reduced form of a redox pair is a strong electron donor with a ___________ affinity for electrons, it is easily oxidized; the oxidized member of such a redox pair is a ____________ electron acceptor.

high, negative, favorable, low, weak

Match the general type of biochemical reaction catalyzed in the left column with the class of enzyme listed in the column on the right. adds phosphate groups to molecules joins two ends of DNA together hydrolyzes peptide bonds rearranges bonds within a single molecule catalyzes the synthesis of polymers such as RNA and DNA catalyzes reactions in which one molecule is oxidized and another is reduced hydrolyzes ATP hydrolyzes bonds between nucleotides removes a phosphate group from a molecule

kinase, ligase, protease, isomerase, polymerase, oxido-reductase, ATPase, nuclease, phosphatase

For a cell's genetic material to be used, the information is first copied from the DNA into the nucleotide sequence of RNA in a process called _________________. Various kinds of RNA are produced, each with different functions. _________________ molecules code for proteins, _________________ molecules act as adaptors for protein synthesis, ________________ molecules are integral components of the ribosome, and _______________ molecules are important in the splicing of RNA transcripts.

transcription, mRNA, tRNA, rRNA, snRNA

Indicate whether the following statements are true or false. 3. Glycolipids lack the glycerol component found in phospholipids _________.

true

Much of the glyceraldehyde 3-phosphate made in the chloroplast ends up producing the molecules needed by the mitochondria to produce ATP. Select one: True False

true

Ribulose 1,5-bisphosphate is similar to oxaloacetate in the Krebs cycle in that they are both regenerated at the end of their respective cycles. Select one: True False

true

Stage 2 of photosynthesis involves a cycle of reactions that does not directly depend on energy derived from sunlight Select one: True False

true

Transcription in bacteria differs from transcription in a eukaryotic cell because __________________________. Select one: a. RNA polymerase (along with its sigma subunit) can initiate transcription on its own. b. RNA polymerase (along with its sigma subunit) requires the general transcription factors to assemble at the promoter before polymerase can begin transcription. c. the sigma subunit must associate with the appropriate type of RNA polymerase to produce mRNAs. d. RNA polymerase must be phosphorylated at its C-terminal tail for transcription to proceed.

Where does most new membrane synthesis take place in a eukaryotic cell? Select one: a. in the endoplasmic reticulum b. in the plasma membran c. on ribosomes d. in the Golgi apparatus e. in the mitochondria

How many replication forks are formed when an origin of replication is opened? Select one: a. 1 b. 2 c. 3 d. 4

Indicate whether the following statements are true or false. 1. Although cholesterol is a hydrophobic molecule, it has a hydrophilic head group like all other membrane lipids ___ _____

true

The instructions specified by the DNA will ultimately specify the sequence of proteins. This process involves DNA, made up of ________ different nucleotides, which gets________________ into RNA, which is then ________________ into proteins, made up of _______ different amino acids. In eukaryotic cells, DNA gets made into RNA in the_______________, while proteins are produced from RNA in the_______________. The segment of DNA called a ________________ is the portion that is copied into RNA; this process is catalyzed by RNA _______________.

4, transcribed, translated, 20, nucleus, cytoplasm, gene, polymerase

A covalent bond between two atoms is formed as a result of the ______________. Select one: 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.

According to current thinking, the minimum requirement for life to have originated on Earth was the formation of a _______________. Select one: a. molecule that could catalyze its own replication. b. molecule that could provide a template for the production of a complementary molecule. c. molecule that could direct protein synthesis. d. double-stranded DNA helix.

Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell. Which of the following ions is the most abundant inside a typical mammalian cell? Select one: a. K+ b. Cl- c. Na+ d. Ca2+

Chemical reactions carried out by living systems depend on the ability of some organisms to capture and use atoms from nonliving sources in the environment. The specific subset of these reactions that break down nutrients in food can be described as _____________. Select one: a. catabolic b. metabolic. c. anabolic. d. symbolic

Correctly finish the following statement: "A cell's genome is _________________." Select one: a. contains all of a cell's DNA. b. is defined as all the genes being used to make protein. c. is altered during embryonic development. d. constantly changes, depending upon the cell's environment.

During nervous-system development in Drosophila, the membrane-bound protein Delta acts as an inhibitory signal to prevent neighboring cells from developing into neuronal cells. Delta is involved in ______________ signaling. Select one: a. contact-dependent b. endocrine c. neuronal d. paracrine

During respiration, energy is retrieved from the high-energy bonds found in certain organic molecules. Which of the following, in addition to energy, are the ultimate products of respiration? Select one: a. CO2, H2O b. CH3, H2O c. CH2OH, O2 d. CO2, O2

Genes in eukaryotic cells often have intronic sequences coded for within the DNA. These sequences are ultimately not translated into proteins. Why? Select one: a. Intronic sequences are removed from RNA molecules by the spliceosome, which works in the nucleus. b. Introns are not transcribed by RNA polymerase. c. Introns are removed by catalytic RNAs in the cytoplasm. d. The ribosome will skip over intron sequences when translating RNA into protein.

Glyceraldehyde 3-phosphate dehydrogenase operates by stripping a hydride ion from its substrate. Which molecule is the recipient of the proton and two electrons during this transfer? Select one: a. NAD+ b. acetyl CoA c. oxygen d. FADH

In anaerobic conditions, skeletal muscle produces _____________. Select one: a. lactate only. b. ethanol and CO2. c. lactate and CO2. d. ethanol only.

In the case of a simple conversion reaction such as XàY, which value of ΔG° is associated with a larger concentration of X than Y at equilibrium? (Hint: How is ΔG° related to K?) Select one: a. ΔG° = 1 b. ΔG° = -1 c. ΔG° = -5 d. ΔG° = 0

In the electron-transport chain in chloroplasts, ________-energy electrons are taken from__________. Select one: a. low; H2O. b. high; H2O. c. low; NADPH . d. high; NADPH

Indicate whether the following statement is true or false. Carbon fixation can be described as a process by which gaseous carbon-containing molecules are captured and incorporated into biological hydrocarbon molecules. Select one: a. True b. False

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

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? Select one: a. anchors b. receptors c. enzymes d. channels

NADH and NADPH are activated carrier molecules that function in completely different metabolic reactions. Both carry two additional ________ and one additional _____________. This combination can also be referred to as a hydride ion. Select one: a. electrons, proton. b. electrons, phosphate. c. hydrogens, electron. d. protons, electron.

New membrane phospholipids are synthesized by enzymes bound to the _____________side of the _________________ membrane. Select one: a. cytosolic, endoplasmic reticulum b. cytosolic, mitochondrial c. luminal, Golgi d. extracellular, plasma

Oxidation is the process by which oxygen atoms are added to a target molecule. Generally, the atom that is oxidized will experience which of the following with respect to the electrons in its outer shell? Select one: a. a net loss b. a net gain c. no change d. an equal sharing

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? Select one: a. water b. molecular oxygen c. methane d. propane

Polypeptides are synthesized from amino acid building blocks. The condensation reaction between the growing polypeptide chain and the next amino acid to be added involves the loss of ________________. Select one: a. a water molecule b. a carboxylic acid group c. an amino group d. a carbon atom

Porin proteins form large, barrel-like channels in the membrane. Which of the following is not true about these channels? Select one: 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.

Prokaryotic cells are able to evolve very fast. For example, under ideal conditions, E.coli can divide as quickly as every 20 minutes. This ability to proliferate helps them to rapidly adapt to new food sources and develop resistance to antibiotics. Which of the options below lists the three main characteristics that support the rapid evolution of prokaryotic populations? Select one: a. large population, rapid growth, can exchange DNA b. microscopic, motile, anaerobic c. aerobic, motile, rapid growth d. no organelles, cell wall, can exchange DNA

Proteins are important architectural and catalytic components within the cell. They help to determine its chemistry, its shape, and its ability to respond to changes in the environment. Remarkably, all of the different proteins in a cell are made from the same 20 __________. By linking them in different sequences, the cell can make protein molecules with different conformations and surface chemistries, and therefore different functions. Select one: a. amino acids b. fatty acids c. nucleotides. d. sugars.

Select the best option to fill in the blanks of the following statement: Fermentation is a/an _____________________ process that converts _____________ into carbon dioxide and _____________________. Select one: a. anaerobic, pyruvate, ethanol b. anaerobic, lactate, ethanol c. eukaryotic, glyceraldehyde 3-phosphate, ethanol d. prokaryotic, lactate, propanol

Several different classes of enzymes are needed for the catabolism of carbohydrates. Which of the following descriptions best matches the function of an isomerase? Select one: a. An enzyme that catalyzes the rearrangement of bonds within a single molecule. b. An enzyme that catalyzes the addition of phosphate groups to other molecules. c. An enzyme that catalyzes the oxidation of a molecule by removing a hydride ion. d. An enzyme that catalyzes a change in the position of a specific chemical group within a single molecule.

Stage 2 of photosynthesis, sometimes referred to as the dark reactions, involves the reduction of CO2 to produce organic compounds such as sucrose. What cofactor is the electron donor for carbon fixation? Select one: a. NADPH b. H2O c. NADH d. FADH2

The correct folding of proteins is necessary to maintain healthy cells and tissues. Unfolded proteins are responsible for such neurodegenerative disorders as Alzheimer'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? Select one: a. They form protein aggregates b. They form structured filaments c. They bind a different target protein. d. They are degraded

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 Select one: a. oligosaccharide b. aminophospholipid c. polysaccharide d. sphingolipid

The enzyme ribulose bisphosphate carboxylase (Rubisco) normally adds carbon dioxide to ribulose 1,5-bisphosphate. However, it will also catalyze a competing reaction in which O2 is added to ribulose 1,5-bisphosphate to form 3-phosphoglycerate and phosphoglycolate. Assume that phosphoglycolate is a compound that cannot be used in any further reactions. If O2 and CO2 have the same affinity for Rubisco, which of the following is the lowest ratio of CO2 to O2 at which a net synthesis of sugar can occur? Select one: a. 3:1 b. 1:3 c. 1:2 d. 2:1

The study of enzyme kinetics is usually performed with purified components and requires the characterization of several aspects of the reaction, including the rate of association with the substrate, the rate of catalysis, and _____________. Select one: a. the regulation of the enzyme activity b. the subcellular localization of the enzyme. c. the enzyme's structure. d. the optimal pH of the reaction.

Transporters, in contrast to channels, work by ________________. Select one: a. specific binding to solutes. b. a gating mechanism. c. filtering solutes by charge. d. filtering solutes by size.

Two or three α helices can sometimes wrap around each other to form coiled-coils. The stable wrapping of one helix around another is typically driven by ________________interactions. Select one: a. hydrophobic b. van der Waals c. ionic d. hydrophilic

What part of the DNA replication process would be most directly affected if a strain of bacteria lacking helicase were used to make the cell extracts? Select one: a. initiation of DNA synthesis b. Okazaki fragment synthesis c. leading-strand elongation d. lagging-strand completion

When a signal needs to be sent to most cells throughout a multicellular organism, the signal most suited for this is a ___________. Select one: a. hormone b. neurotransmitter . c. dissolved gas . d. scaffold .

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

Which of the following elements is least abundant in living organisms? Select one: a. sulfur b. oxygen c. carbon d. nitrogen

Which of the following is not a feature commonly observed in α-helices? Select one: a. left-handedness b. one helical turn every 3.6 amino acids c. amino acid side chains that point outward d. cylindrical shape

Which of the following membrane lipids does not contain a fatty acid tail? Select one: a. cholesterol b. phosphatidylcholine c. phosphatidylserine d. a glycolipid

Which of the following molecules of RNA would you predict to be the most likely to fold into a specific structure as a result of intramolecular base-pairing? Select one: a. 5′-CCCUAAAAAAAAAAAAAAAAUUUUUUUUUUUUUUUUAGGG-3′ b. 5′-UGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUG-3′ c. 5′-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA-3′ d. 5′-GGAAAAGGAGAUGGGCAAGGGGAAAAGGAGAUGGGCAAGG-3′

Which of the following statements about the cell cycle is false? Select one: a. Once a cell decides to enter the cell cycle, the time from start to finish is the same in all eukaryotic cells. b. An unfavorable environment can cause cells to arrest in G1. c. A cell has more DNA during G2 than it did in G1. d. The cleavage divisions that occur in an early embryo have short G1 and G2 phases

Which of the following statements is not true about the possible fates of glyceraldehyde 3-phosphate? Select one: a. It can be transported into the thylakoid space for use as a secondary electron acceptor downstream of the electron-transport chain b. It can be exported from the chloroplast to the cytosol for conversion into sucrose c. It can be used as a precursor for fatty acid synthesis and stored as fat droplets in the stroma d. It can be used to make starch, which is stored inside the stroma of the chloroplast

Which type of lipids are the most abundant in the plasma membrane? Select one: a. phospholipids b. glycolipids c. sterols d. triacylglycerides

Which of the following statements best reflects the nature of synaptic plasticity? Select one: a. Synaptic response changes in magnitude depending on frequency of stimulation. b. There is a change in the type of neurotransmitter used at the synapse. c. New synapses are created due to the postnatal generation of neurons. d. Neuronal connections are pruned during normal development.

Which of the following does not occur before a eukaryotic mRNA is exported from thenucleus? Select one: a. The ribosome binds to the mRNA. b. The mRNA is polyadenylated at its 3′end c. 7-methyl guanosine is added in a 5′-to-5′ linkage to the mRNA. d. RNA polymerase dissociates.

a; (a) Ribosomes are in the cytosol and will bind to the mRNA once it has been exported from the nucleus.

Glycolysis generates more stored energy than it expends. What is the net number of activated carrier molecules produced in this process (number and type of molecules produced minus the number of those molecules used as input)? Select one: a. 2 ATP, 2 NADH b. 4 ATP, 4 NADH c. 6 ATP, 2 NADH d. 4 ATP, 2 NADH

a; Although 4 ATP and 2 NADH are produced, 2 ATP are converted to ADP in the early steps of glycolysis. In contrast, NADH is not converted to NAD+ in any of the reactions.

Which of the following channels would not be expected to generate a change in voltage by movement of its substrate across the membrane where it is found? Select one: a. an aquaporin b. a sodium channel c. a calcium channel d. proton channel

a; Aquaporin channels are found in the plasma membrane of some cells, where they facilitate diffusion of water across the membrane. Because water is an uncharged molecule, its movement would not be expected to alter the voltage across the membrane.

Which of the following statements about prokaryotic mRNA molecules is false? Select one: a. Ribosomes must bind to the 5′cap before initiating translation. b. Ribosomes can start translating an mRNA molecule before transcription is complete. c. A single prokaryotic mRNA molecule can be translated into several proteins. d. mRNAs are not polyadenylated.

a; Bacterial mRNAs do not have 5′caps. Instead, ribosome-binding sites upstream of the start codon tell the ribosome where to begin searching for the start of translation.

What part of the DNA replication process would be most directly affected if a strain of bacteria lacking primase were used to make the cell extracts? Select one: a. initiation of DNA synthesis b. Okazaki fragment synthesis c. leading-strand elongation d. lagging-strand completion

a; Choice (a) is the best answer because DNA synthesis cannot begin without the initial primers.

Glycolysis is an anaerobic process used to catabolize glucose. What does it mean for this process to be anaerobic? Select one: a. no oxygen is required b. no oxidation occurs c. it takes place in the lysosome d. glucose is broken down by the addition of electrons

a; Glycolysis takes place in the cytosol, and although oxidation of glucose is taking place, no molecular oxygen is used.

The advantage to the cell of the gradual oxidation of glucose during cellular respiration compared with its combustion to CO2 and H2O in a single step is that ________________. Select one: a. energy can be extracted in usable amounts. b. no energy is lost as heat. c. more CO2 is produced for a given amount of glucose oxidized. d. more free energy is released for a given amount of glucose oxidize

a; The amount of free energy released by glucose oxidation is the same as combustion, the amount of CO2 released is the same, and some of the energy released is still lost as heat, whatever the route.

The citric acid cycle is a series of oxidation reactions that removes carbon atoms from substrates in the form of CO2. Once a molecule of acetyl CoA enters the citric acid cycle, how many complete cycles are required for both of the carbon atoms in its acetyl group to be oxidized to CO2? Select one: a. 4 b. 2 c. 3 d. 1

a; The carbons from acetyl CoA are carried through the entire first reaction cycle. In the second cycle, one of these carbons is oxidized to CO2. Two more cycles later, the second carbon molecule from that same acetyl CoA is oxidized to CO2

The Na+-K+ ATPase is also known as the Na+-K+ pump. It is responsible for maintaining the high extracellular sodium ion concentration and the high intracellular potassium ion concentration. What happens immediately after the pump hydrolyzes ATP? Select one: a. the pump is phosphorylated b. ADP is bound c. Na+ is bound d. the pump changes conformation

a; The phosphorylation of the pump causes the conformational change, and it occurs after the binding of Na+.

A poison added to an in vitro translation mixture containing mRNA molecules with the sequence 5′-AUGAAAAAAAAAAAAUAA-3′ has the following effect: the only product made is a Met-Lys dipeptide that remains attached to the ribosome. What is the most likely way in which the poison acts to inhibit protein synthesis? Select one: a. It mimics release factor. b. It inhibits movement of the small subunit relative to the large subunit. c. It inhibits release factor. d. It inhibits peptidyl transferase activity.

Activated carriers are small molecules that can diffuse rapidly and be used to drive biosynthetic reactions in the cell. Their energy is stored in a readily transferable form such as high-energy electrons or chemical groups. Which of the molecules below is the most widely used activated carrier? Select one: a. NADPH b. ATP c. NADH d. FADH2

All members of the steroid hormone receptor family __________________. Select one: a. are found only in the cytoplasm b. interact with signal molecules that diffuse through the plasma membrane c. do not undergo conformational changes . d. are cell-surface receptors

Catalysts are molecules that lower the activation energy for a given reaction. Cells produce their own catalysts called _____________. Select one: a. proteins. b. enzymes c. cofactors d. complexes.

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. Select one: a. polar b. amphipathic c. oxygen-containing d. hydrophobic

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

DNA polymerases are processive, which means that they remain tightly associated 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? Select one: a. helicase b. sliding clamp c. single-strand binding protein d. primase

If you add a compound to illuminated chloroplasts that inhibits the NADP+ reductase, NADPH generation ceases, as expected. However, ferredoxin does not accumulate in the reduced form because it is able to donate its electrons not only to NADP+ (via NADP+ reductase) but also back to the cytochrome b6-f complex. Thus, in the presence of the compound, a "cyclic" form of photosynthesis occurs in which electrons flow in a circle from ferredoxin, to the cytochrome b6-f complex, to plastocyanin, to photosystem I, to ferredoxin. What will happen if you now also inhibit photosystem II? Select one: a. Less ATP will be generated per photon absorbed. b. Plastoquinone will accumulate in the oxidized form. c. ATP synthesis will cease. d. Plastocyanin will accumulate in the oxidized form.

In eukaryotes, but not in prokaryotes, ribosomes find the start site of translation by ____________________________. Select one: a. binding directly to a ribosome-binding site preceding the initiation codon. b. scanning along the mRNA from the 5′ end. c. recognizing an AUG codon as the start of translation. d. binding an initiator tRNA.

Initiator proteins bind to replication origins and disrupt hydrogen bonds between the two DNA strands being copied. Which of the factors below does not contribute to the relative ease of strand separation by initiator proteins? Select one: a. replication origins are rich in A-T base pairs b. the reaction can occur at room temperature c. they only separate a few base pairs at a time d. once opened, other proteins of the DNA replication machinery bind to the origin

Membranes only allow certain molecules or ions to pass through. This is called______. Select one: a. Diffusion discrepancy b. Selectively permeable c. Transmembrane spanning selection d. Membrane specificity

Mitochondria perform cellular respiration, a process that uses oxygen, generates carbon dioxide, and produces chemical energy for the cell (which we will learn about later on in this semester). Which answer below indicates a correct pairing of material "burned" and the form of energy produced during cellular respiration? Select one: a. fat, protein b. sugar, ATP c. sugar, fat d. fat, ADP

Protein folding can be studied using a solution of purified protein and a denaturant (urea), a solvent that interferes with noncovalent interactions. Which of the following is observed after the denaturant is removed from the protein solution? Select one: a. The polypeptide remains denatured. b. The polypeptide returns to its original conformation. c. The polypeptide forms solid aggregates and precipitates out of solution. d. The polypeptide adopts a new, stable conformation.

Pumps are transporters that are able to harness energy provided by other components in the cells to drive the movement of solutes across membranes, against their concentration gradient. This type of transport is called _____________. Select one: a. facilitated diffusion . b. active transport c. free diffusion . d. passive transport .

The DNA duplex consists of two long covalent polymers wrapped around each other many times over their entire length. The separation of the DNA strands for replication causes the strands to be "overwound"in front of the replication fork. How does the cell relieve the torsional stress created along the DNA duplex during replication? Select one: a. Nothing needs to be done because the two strands will be separated after replication is complete. b. Topoisomerases break the covalent bonds of the backbone allowing the local unwinding of DNA ahead of the replication fork. c. Helicase unwinds the DNA and rewinds it after replication is complete. d. DNA repair enzymes remove torsional stress as they replace incorrectly paired bases.

The citric acid cycle is a series of oxidation reactions that removes carbon atoms from substrates in the form of CO2. Where do the oxygen atoms in the carbon dioxide molecules come from? Select one: a. phosphates b. water c. molecular oxygen d. acetyl CoA

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? Select one: a. nucleosome core particles b. linker histones c. core histones d. linker DNA Feedback

The classic experiments conducted by Meselson and Stahl demonstrated that DNA replication is accomplished by employing a ________________ mechanism. Select one: a. continuous b. semiconservative c. dispersive d. conservative

The flow of genetic information is controlled by a series of biochemical reactions that result in the production of proteins, each with its own specific order of amino acids. This is often called the central dogma of biology. Please choose the correct series of biochemical reactions from the options presented here that reflect the central dogma. Select one: a. translation, replication, transcription b. replication, transcription, translation c. translation, transcription, replication d. replication, translation, transcription

The human genome is a diploid genome. However, when germ-line cells produce gametes, these specialized cells are haploid. What is the total number of chromosomes found in each of the gametes (egg or sperm) in your body? Select one: a. 46 b. 23 c. 44 d. 22 Feedback

The oxygen-dependent reactions required for cellular respiration were originally thought to occur in a linear pathway. By using a competitive inhibitor for one enzyme in the pathway, investigators discovered that these reactions occur in a cycle. Which enzyme was inhibited? Select one: a. malate dehydrogenase b. succinate dehydrogenase c. isocitrate dehydrogenase d. aconitase

The phosphorylation of a protein is typically associated with a change in activity, the assembly of a protein complex, or the triggering of a downstream signaling cascade. The addition of ubiquitin, a small polypeptide, is another type of covalent modification that can affect the protein function. Ubiquitylation often results in ______________. Select one: a. membrane association . b. protein degradation . c. nuclear translocation . d. protein secretion

The potential energy stored in high-energy bonds is commonly harnessed when the bonds are split by the addition of _______________ in a process called _____________. Select one: a. ATP, phosphorylation. b. water, hydrolysis. c. hydroxide, hydration. d. acetate, acetylation.

The second law of thermodynamics states that the disorder in any system is always increasing. In simple terms, you can think about dropping NaCl crystals into a glass of water. The solvation and diffusion of ions is favored because there is an increase in _____________. Select one: a. pH. b. entropy c. ions. d. stored energy.

To study how proteins fold, scientists must be able to purify the protein of interest, use solvents to denature the folded protein, and observe the process of refolding at successive time points. What is the effect of the solvents used in the denaturation process? Select one: a. The solvents break all covalent interactions b. The solvents break all noncovalent interactions. c. The solvents break some of the noncovalent interactions resulting in a misfolded protein. d. The solvents create a new protein conformation.

What part of the DNA replication process would be most directly affected if a strain of bacteria lacking single-strand binding protein were used to make the cell extracts? Select one: a. initiation of DNA synthesis b. Okazaki fragment synthesis c. lagging-strand completion d. leading-strand elongation

What unit of length would you generally use to measure a typical plant or animal cell? Select one: a. nanometers b. micrometers c. centimeters d. millimeters

When elemental sodium is added to water, the sodium atoms ionize spontaneously. Uncharged Na becomes Na+. This means that the Na atoms have been _____________. Select one: a. protonated. b. oxidized c. hydrogenated. d. reduced.

Which of the following best describes the behavior of a gated channel? Select one: a. It opens more widely as the stimulus becomes stronger. b. It opens more frequently in response to a given stimulus. c. It stays open continuously when stimulated. d. It remains closed if unstimulated

Which of the following is not a feature commonly observed in βsheets? Select one: a. extended polypeptide backbone b. coiled-coil patterns c. parallel regions d. antiparallel regions Feedback

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 of the following phenomena will be observed if a cell's membrane is pierced? Select one: a. the membrane collapses b. the membrane reseals c. the membrane expands d. a tear is formed

Which of the following processes do not take place in the mitochondria? Select one: a. oxidation of fatty acids to acetyl CoA b. glycogen breakdown c. citric acid cycle d. conversion of pyruvate to activated acetyl groups

Which of the following statements about sequence proofreading during DNA replication is false? Select one: a. The exonuclease activity is in a different domain of the DNA polymerase. b. The exonuclease activity cleaves DNA in the 5′-to-3′ direction. c. The DNA proofreading activity occurs concomitantly with strand elongation. d. If an incorrect base is added, it is "unpaired" before removal.

Which of the following statements about the genetic code is correct? Select one: a. All codons specify more than one amino acid. b. The genetic code is redundant. c. All amino acids are specified by more than one codon. d. All codons specify an amino acid.

Which of the following statements is false? Select one: a. If two genes are to be expressed in a cell, these two genes can be transcribed with different efficiencies. b. Unlike DNA, RNA uses a uracil base and a deoxyribose sugar. c. A new RNA molecule can begin to be synthesized from a gene before the previous RNA molecule's synthesis is completed. d. RNA polymerase is responsible for both unwinding the DNA helix and catalyzing the formation of the phosphodiester bonds between nucleotides.

Which of the following statements is true with respect to this in vitro replication system? Select one: a. There will be only one leading strand and one lagging strand produced using this template. b. The leading and lagging strands compose one half of each newly synthesized DNA strand. c. The DNA replication machinery can assemble at multiple places on this plasmid. d. One daughter DNA molecule will be slightly shorter than the other .

Which of the following statements is true? Select one: a. Peptide bonds are the only covalent bonds that can link together two amino acids in proteins b. Nonpolar amino acids tend to be found in the interior of proteins. c. The polypeptide backbone is free to rotate about each peptide bond. d. The sequence of the atoms in the polypeptide backbone varies between different proteins.

Which of the following statements is true? Select one: a. Ribosomes are synthesized entirely in the cytoplasm. b. rRNA contains the catalytic activity that joins amino acids together. c. Ribosomes are large RNA structures composed solely of rRNA. d. A ribosome binds one tRNA at a time.

Which one of the following is the main reason that a typical eukaryotic gene is able to respond to a far greater variety of regulatory signals than a typical prokaryotic gene or operon? Select one: a. Eukaryotic RNA polymerases require general transcription factors. b. The transcription of a eukaryotic gene can be influenced by proteins that bind far from the promoter. c. Prokaryotic genes are packaged into nucleosomes. d. Eukaryotes have three types of RNA polymerase

Which subatomic particles can vary between isotopes of the same element, without changing the observed chemical properties? Select one: a. neutrons and electrons b. neutrons c. electrons d. protons and neutrons

You have a piece of DNA that includes the following sequence: 5′-ATAGGCATTCGATCCGGATAGCAT-3′ 3′-TATCCGTAAGCTAGGCCTATCGTA-5′ Which of the following RNA molecules could be transcribed from this piece of DNA? Select one: a. 5′-UAUCCGUAAGCUAGGCCUAUGCUA-3′ b. 5′-AUAGGCAUUCGAUCCGGAUAGCAU-3′ c. 5′-UACGAUAGGCCUAGCUUACGGAUA-3′ d. none of the above

Your body extracts energy from the food you ingest by catalyzing reactions that essentially "burn" the food molecules in a stepwise fashion. What is another way to describe this process? Select one: a. reduction b. oxidation c. dehydration d. solvation

In eukaryotes, but not in prokaryotes, ribosomes find the start site of translation by ____________________________. Select one: a. recognizing an AUG codon as the start of translation. b. scanning along the mRNA from the 5′ end. c. binding an initiator tRNA. d. binding directly to a ribosome-binding site preceding the initiation codon.

Which of the following cells rely exclusively on glycolysis to supply them with ATP? Select one: a. skeletal muscle cells b. anaerobically growing yeast c. plant cells d. aerobic bacteria

b; All the other cells can perform oxidative phosphorylation to generate additional ATP.

Which amino acid would you expect a tRNA with the anticodon 5′-CUU-3′ to carry? Select one: a. phenylalanine b. lysine c. glutamic acid d. leucine

b; As is conventional for nucleotide sequences, the anticodon is given reading from 5′to3′. The complementary base -pairing occurs between antiparallel nucleic acid sequences, and the codon recognized by this anticodon will therefore be 5'-AAG-3′.

Active transport requires the input of energy into a system so as to move solutes against their electrochemical and concentration gradients. Which of the following is not one of the common ways to perform active transport? Select one: a. light-driven b. K+-coupled c. ATP-driven d. Na+-coupled

b; Because K+ is a positively charged ion and the outside of the plasma membrane is positively charged, K+ has a very small electrochemical gradient across the membrane even though its concentration gradient is large. Because there is little net movement across the membrane for K+, it would not make a good source of energy to drive the transport of other molecules against their respective gradients.

There are several reasons why the primase used to make the RNA primer for DNA replication is not suitable for gene transcription. Which of the statements below is not one of those reasons? Select one: a. Primase initiates RNA synthesis on a single-stranded DNA template. b. Primase can initiate RNA synthesis without the need for a base-paired primer. c. Primase synthesizes only RNAs of about 5-20 nucleotides in length. d. The RNA synthesized by primase remains base-paired to the DNA template.

b; Choice (b) is true for both primase and RNA polymerase, so it does not describe why primase cannot be used for gene transcription.

Below is a list of molecules with different chemical characteristics. Knowing that all molecules will eventually diffuse across a phospholipid bilayer, select the option below that most accurately predicts the relative rates of diffusion of these molecules (fastest to slowest). alanine estrogen propanol sodium Select one: a. estrogen > propanol > sodium > alanine b. sodium > propanol > alanine> estrogen c. alanine> propanol > sodium > estrogen d. estrogen > propanol > alanine> sodium

d; Estrogen is a steroid hormone and will diffuse the fastest across the membrane. Propanol is a small, uncharged molecule with a polar group. Alanine is an amino acid, and although it has a small, nonpolar side group, amino acids are charged molecules. Sodium is an ion and will move the slowest across the bilayer.

Cells require one particular monosaccharide as a starting material to synthesize nucleotide building blocks. Which of the monosaccharides below fills this important role? Select one: a. fructose b. glucose c. ribose d. ribulose

Chemical reactions that lead to a release of free energy are referred to as "energetically favorable." Another way to describe these reactions is: _____________. Select one: a. uphill. b. uncatalyzed. c. spontaneous d. activated.

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

DNA replication is considered semiconservative because ___________________________. Select one: a. after many rounds of DNA replication, the original DNA double helix is still intact . b. each daughter DNA molecule consists of two new strands copied from the parent DNA molecule . c. each daughter DNA molecule consists of one strand from the parent DNA molecule and one new strand . d. new DNA strands must be copied from a DNA template

Energy cannot be created or destroyed, but it can be converted into other types of energy. Cells use potential kinetic energy to generate stored chemical energy in the form of activated carrier molecules, which are often employed to join two molecules together in _____________ reactions. Select one: a. oxidation b. hydrolysis c. condensation d. reduction

In a DNA double helix, _____________________. Select one: a. the two DNA strands are identical b. purines pair with purines c. the two DNA strands run antiparallel d. thymine pairs with cytosine

In stage 1 of photosynthesis, a proton gradient is generated and ATP is synthesized. Where do protons become concentrated in the chloroplast? Select one: a. thylakoid membrane b. stroma c. thylakoid space d. inner membrane

In step 1 of the citric acid cycle, citrate is generated by the enzyme citrate synthase. The enzyme combines the two-carbon acetyl group from acetyl CoA and the four-carbon oxaloacetate. What is the source of energy that drives this reaction forward? Select one: a. a high-energy phosphodiester bond b. a transfer of high-energy electrons c. a high-energy thioester bond d. the heat of molecular collision

Molecular chaperones can work by creating an "isolation chamber." What is the purpose of this chamber? Select one: a. This chamber is used to increase the local protein concentration, which will help speed up the folding process. b. The chamber acts as a garbage disposal, degrading improperly folded proteins so that they do not interact with properly folded proteins. c. This chamber serves to protect unfolded proteins from interacting with other proteins in the cytosol, until protein folding is completed d. This chamber serves to transport unfolded proteins out of the cell

Oxidation and reduction states are relatively easy to determine for metal ions, because there is a measurable net charge. In the case of carbon compounds, oxidation and reduction depend on the nature of polar covalent bonds. Which of the following is the best way to describe these types of bond? Select one: a. hydrogen bonds in a nonpolar solution b. covalent bonds in an aqueous solution c. unequal sharing of electrons across a covalent bond d. equal sharing of electrons across a covalent bond

Photosynthesis is a process that takes place in chloroplasts and uses light energy to generate high-energy electrons, which are passed along an electron-transport chain. Where are the proteins of the electron-transport chain located in chloroplasts? Select one: a. thylakoid space b. inner membrane c. thylakoid membrane d. stroma

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." Select one: a. a complex of more than one polypeptide chain b. the tertiary structure of a substrate-binding pocket c. a protein segment that folds independently d. a small cluster of α helices and β sheets

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? Select one: a. on the surface of the protein b. buried in the interior of the protein c. inside a cavity on the protein surface d. forms on the surface of the protein in the presence of ligand

Pyruvate must move from the cytosol into the mitochondria, where it is oxidized to form CO2 and acetyl CoA by the pyruvate dehydrogenase complex. How many different enzymes and what total number of polypeptides, respectively, are required to perform this oxidation process in the mitochondrion? Select one: a. 1; 60 b. 3; 3 c. 3; 60 d. 3; 26

RNA in cells differs from DNA in that ___________________. Select one: a. it contains the base uracil, which pairs with cytosine . b. it is single-stranded and cannot form base pairs . c. it is single-stranded and can fold up into a variety of structures. d. the sugar ribose contains fewer oxygen atoms than does deoxyribose

The chromatin structure in eukaryotic cells is much more complicated than that observed in prokaryotic cells. This is thought to be the reason that DNA replication occurs much faster in prokaryotes. How much faster is it? Select one: a. 2× b. 5× c. 10× d. 100×

The photosystems in chloroplasts contain hundreds of chlorophyll molecules, most of which are part of _______________. Select one: a. the reaction center. b. the ferredoxin complex. c. the antenna complex. d. plastoquinone

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? Select one: a. import/export of molecules b. cellular movement c. selective permeability d. intercellular communication

The process of DNA replication requires that each of the parental DNA strands be used as a ___________________ to produce a duplicate of the opposing strand. Select one: a. catalyst b. competitor c. template d. copy

The ribosome is important for catalyzing the formation of peptide bonds. Which of the following statements is true? Select one: a. The number of rRNA molecules that make up a ribosome greatly exceeds the number of protein molecules found in the ribosome. b. The large subunit of the ribosome is important for binding to the mRNA. c. The catalytic site for peptide bond formation is formed primarily from an rRNA. d. Once the large and small subunits of the ribosome assemble, they will not separate from each other until degraded by the proteasome

The sigma subunit of bacterial RNA polymerase ___________________. Select one: a. contains the catalytic activity of the polymerase b. remains part of the polymerase throughout transcription c. recognizes promoter sites in the DNA d. recognizes transcription termination sites in the DNA

The stimulation of a motor neuron ultimately results in the release of a neurotransmitter at the synapse between the neuron and a muscle cell. What type of neurotransmitter is used at these neuromuscular junctions? Select one: a. glutamate b. glycine c. acetylcholine d. GABA

The study of enzymes also includes an examination of how the activity is regulated. Molecules that can act as competitive inhibitors for a specific reaction are often similar in shape and size to the enzyme's substrate. Which variable(s) used to describe enzyme activity will remain the same in the presence and absence of a competitive inhibitor? Select one: a. Vmax and Km b. Km c. Vmax d. V

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) Select one: a. 16 carbons with no double bonds b. 24 carbons with 1 double bond c. 15 carbons with 2 double bonds d. 20 carbons with 2 double bonds

Which of the following best describes the mechanism by which chromatin-remodeling complexes "loosen" the DNA wrapped around the core histones? Select one: a. They chemically modify core histones to alter the affinity between the histone octamer and the DNA. b. They remove histone H1 from the linker DNA adjacent to the core histone octamer. c. They use energy derived from ATP hydrolysis to change the relative position of the DNA and the core histone octamer. d. They chemically modify the DNA, changing the affinity between the histone octamer and the DNA.

Which of the following statements about resting membrane potential is not true? Select one: a. The resting membrane potential for most animal cells is 0 mV, because the positive and negative ions are in balance. b. The resting membrane potential for most animal cells is positive, because Na+ ions are so plentiful inside cells. c. The resting membrane potential for most animal cells is negative, because the inside of the cell is more negatively charged than the outside of the cell. d. At the resting membrane potential, no ions enter or exit the cell.

Which of the following statements about the cytoskeleton is true? Select one: a. All eukaryotic cells have actin, microtubules, and intermediate filaments in their cytoplasm. b. The three cytoskeletal filaments perform distinct tasks in the cell and act completely independently of one another. c. Actin filaments and microtubules have an inherent polarity, with a plus end that grows more quickly than the minus end. d. The cytoskeleton provides a rigid and unchangeable structure important for the shape of the cell.

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

Which statement is NOT true about mutations? Select one: a. A mutation is a change in the DNA that can generate offspring that are as fit for survival as their parents are. b. A mutation can be a result of imperfect DNA duplication. c. A mutation is a result of sexual reproduction. d. A mutation is a change in the DNA that can generate offspring less fit for survival than their parents.

Which subatomic particles contribute to the atomic number for any given element? Select one: a. protons and neutrons b. protons and electrons c. protons d. neutrons

You are a virologist interested in studying the evolution of viral genomes. You are studying two newly isolated viral strains and have sequenced their genomes. You find that the genome of strain 1 contains 25% A, 55% G, 20% C, and 10% T. You report that you have isolated a virus with a single-stranded DNA genome. Based on what evidence can you make this conclusion? Select one: a. single-stranded genomes always have a large percentage of purines b. using the formula: G-A = C + T c. Double-stranded genomes have equal amounts of A and T d. Single-stranded genomes have a higher rate of mutation

Which of the following statements about the cytoskeleton is false? Select one: a. The cytoskeleton controls the location of organelles in eukaryotic cells. b. The cytoskeleton of a cell can change in response to the environment. c. Covalent bonds between protein monomers hold together cytoskeletal filaments. d. The cytoskeleton is made up of three types of protein filaments.

c; The protein monomers of the cytoskeleton are held together by noncovalent interactions between the protein monomers. All other statements are true.

Which of the following is not a feature commonly observed in α helices? Select one: a. one helical turn every 3.6 amino acids b. cylindrical shape c. left-handedness d. amino acid side chains that point outward

You have generated antibodies that recognize the extracellular domain of the Ca2+-pump. Adding these antibodies to animal cells blocks the active transport of Ca2+ from the cytosol into the extracellular environment. What do you expect to observe with respect to intracellular Ca2+. Select one: a. Ca2+-pumps in the Golgi apparatus keep cytosolic calcium levels low. b. Ca2+-pumps in vesicle membranes keep cytosolic calcium levels low. c. Ca2+-pumps in the endoplasmic reticulum membrane keep cytosolic calcium levels low. d. Ca2+ concentrations in the cytosol increase at a steady rate.

c; In addition to the Ca2+- pumps in the plasma membrane, Ca2+-pumps are also found in the membrane of the endoplasmic reticulum (ER). Those in the ER membrane will continue to remove calcium ions from the cytosol, keeping calcium levels low.

Which of the following steps or processes in aerobic respiration include the production of carbon dioxide? Select one: a. breakdown of glycogen b. glycolysis c. conversion of pyruvate to acetyl CoA d. oxidative phosphorylation

c; One carbon is oxidized and released as carbon dioxide when pyruvate is converted to acetyl CoA.

Which of the following might decrease the transcription of only one specific gene in a bacterial cell? Select one: a. a decrease in the amount of sigma factor b. a decrease in the amount of RNA polymerase c. a mutation that introduced extensive sequence changes into the DNA that precedes the gene's transcription start site d. a mutation that introduced a stop codon into the DNA that precedes the gene's coding sequence

c; Such changes would probably destroy the function of the promoter, making RNA polymerase unable to bind to it.

A mutation in the tRNA for the amino acid lysine results in the anticodon sequence 5′-UAU-3′ (instead of 5′-UUU-3′). Which of the following aberrations in protein synthesis might this tRNA cause? Select one: a. substitution of lysine for phenylalanine b. substitution of lysine for tyrosine c. substitution of lysine for isoleucine d. read-through of stop codons

c; The mutant tRNA Lys will be able to pair with the codon 5′-AUA-3′, which codes for isoleucine.

By definition, prokaryotic cells do not possess __________. Select one: a. ribosomes. b. replication machinery. c. a nucleus d. membrane bilayers.

The concentration of a particular protein,X,in a normal human cell rises gradually from a low point, immediately after cell division, to a high point, just before cell division, and then drops sharply. The level of its mRNA in the cell remains fairly constant throughout this time. Protein X is required for cell growth and survival, but the drop in its level just before cell division is essential for division to proceed. You have isolateda line of human cells that grow in size in culture but cannot divide, and on analyzing these mutants, you find that levels of X mRNA in the mutant cells are normal. Which of the following mutations in the gene for X could explain these results? Select one: a. the introduction of a stop codon that truncates protein X at the fourth amino acid b. the deletion of a sequence that encodes sites at which ubiquitin can be attached to the protein c. a change at a splice site that prevents splicing of the RNA d. a change of the first ATG codon to CCA

b; The decrease in the level of protein X in the normal cell is most probably due to protein degradation, because levels of mRNA remain constant. The inability of the mutant cell to divide could be due to a mutation that inhibits protein degradation. This would be achieved by the removal of sites for attachment of ubiquitin, which targets proteins for destruction.

Cells make use of H+ electrochemical gradients in many ways. Which of the following proton transporters is used to regulate pH in animal cells? Select one: a. H+ ATPase b. Na+-H+ exchanger c. light-driven pump d. H+ symporter

b; The high extracellular concentration of Na+ is employed by a transporter that pumps protons out of animal cells as Na+ is brought into the cell. The other transporters are found only in bacterial cells.

Which of the following statements about RNA splicing is false? Select one: a. Small RNA molecules in the nucleus perform the splicing reactions necessary for the removal of introns. b. For a gene to function properly, every exon must be removed from the primary transcript in the same fashion on every mRNA molecule produced from the same gene. c. Conventional introns are not found in bacterial genes. d. Splicing occurs after the 5′ cap has been added to the end of the primary transcript.

b; The primary transcript of a gene can sometimes be spliced differently so that different exons can be stitched together to produce distinct proteins in a process called alternative splicing.

Which of the following is required for the secretion of neurotransmitters in response to an action potential? Select one: a. voltage-gated K+ channels b. voltage-gated Ca2+ channels c. Na+-K+ pumps d. neurotransmitter receptors

b; Voltage-gated Ca2+ channels open in response to the depolarization caused as the action potential moves toward the nerve terminal. The influx of calcium from outside the cell causes the synaptic vesicles to fuse with the plasma membrane and release large amounts of neurotransmitter into the synaptic cleft

Which of the following stages in the breakdown of the piece of toast you had for breakfast generates the most ATP? Select one: a. the citric acid cycle b. oxidative phosphorylation c. the digestion of starch to glucose d. glycolysis Feedback

b; is the correct answer. Oxidative phosphorylation produces about 28 ATP molecules.

Which of the following pairs of codons might you expect to be read by the same tRNA as a result of wobble? Select one: a. CUU and UUU b. CAC and CAU c. AAU and AGU d. GAU and GAA

b; is the correct answer. These two codons differ only in the third position and also encode the same amino acid, which is the definition of wobble. Although the codons GAU and GAA [choice (b)] also differ only in the third position, they are unlikely in normal circumstances to be read by the same tRNA, because they encode different amino acids.

1.00 points out of 1.00 Not flaggedFlag question Question text Living systems are incredibly diverse in environment, size, environment, and shape. Estimates are between 10 million and 100 million different species. Despite a wide variety of organisms, it remains difficult to define what it means to say something is alive or has the properties of a living organism. What is defined as the smallest unit of life? Select one: a. protein b. organelle c. cell d. DNA

Acetylcholine is a signaling molecule that elicits responses from heart muscle cells, salivary gland cells, and skeletal muscle cells. Which of the following statements is false? Select one: a. Heart muscle cells, salivary gland cells, and skeletal muscle cells all respond to acetylcholine within minutes of receiving the signal. b. Heart muscle cells decrease their rate and force of contraction when they receive acetylcholine, whereas skeletal muscle cells contract. c. Heart muscle cells, salivary gland cells, and skeletal muscle cells all express an acetylcholine receptor that belongs to the transmitter-gated ion channel family. d. Active acetylcholine receptors on salivary gland cells and heart muscle cells activate different intracellular signaling pathways

You have a segment of DNA that contains the following sequence: 5′-GGACTAGACAATAGGGACCTAGAGATTCCGAAA-3′ 3′-CCTGATCTGTTATCCCTGGATCTCTAAGGCTTT-5′ You know that the RNA transcribed from this segment contains the following sequence: 5′-GGACUAGACAAUAGGGACCUAGAGAUUCCGAAA-3′ Which of the followingchoices best describes how transcription occurs? Select one: a. the top strand is the template strand; RNA polymerase moves along this strand from 5′to 3′ b. the top strand is the template strand; RNA polymerase moves along this strand from 3′ to 5′ c. the bottom strand is the template strand; RNA polymerase moves along this strand from 5′ to 3′ d. the bottom strand is the template strand; RNA polymerase moves along this strand from 3′ to 5′

d; The bottom strand can hybridize with the RNA molecule and thus is the template strand. The polymerase moves along the DNA in a 3′-to-5′ direction, because the RNA nucleotides are joined in a 5′- to-3′ polarity.

Which of the following statements does not accurately describe the events involved in the propagation of an action potential? Select one: a. Local depolarization causes nearby Na+ channels to open. b. An initial influx of Na+ through a small cluster of channels causes local depolarization of the membrane. c. Channels in depolarized regions of the membrane are inactivated until the resting membrane potential is reestablished d. The opening of transmitter-gated K+ channels helps to repolarize the membrane.

d; The outflow of K+ through voltage-gated K+ channels helps bring the membrane back to its resting potential

Below is the sequence from the 3′end of an mRNA. 5′-CCGUUACCAGGCCUCAUUAUUGGUAACGGAAAAAAAAAAAAAA-3′ If you were told that this sequence contains the stop codon for the protein encoded by this mRNA, what is the anticodon on the tRNA in the P site of the ribosome when release factor binds to the A site? Select one: a. 5′-UGG-3′ b. 5′-UUA-3′ c. 5′-CCG-3′ d. 5′-CCA-3′

d; The stop codon (UAA) is underlined in the mRNA sequence below; this is the only stop codon on this piece of mRNA. The codon (UGG) preceding the stop codon will be binding to a tRNA in the P site of the ribosome when release factor binds to the A site. The anticodon of the tRNA will bind to the codon UGG and will be CCA. 5′-CCGUUACCAGGCCUCAUUAUUGGUAACGGAAAAAAAAAAAAAA-3'

Total nucleic acids are extracted from a culture of yeast cells and are then mixed with resin beads to which the polynucleotide 5′-TTTTTTTTTTTTTTTTTTTTTTTTT-3′ has been covalently attached. After a short incubation, the beads are then extracted from the mixture. When you analyze the cellular nucleic acids that have stuck to the beads, which of the following is most abundant? Select one: a. DNA b. tRNA c. rRNA d. mRNA

d; mRNA is the only type of RNA that is polyadenylated, and its poly-A tail would be able to base-pair with the strands of poly T on the beads and thus stick to them. DNA would not be found in the sample, because the poly-A tail is not encoded in the DNA and long runs of T are rare in DNA.

What would be the most obvious outcome of repeated cell cycles consisting of S phase and M phase only? Select one: a. The mitotic spindle could not assemble. b. Cells would not be able to replicate their DNA. c. Cells would get larger and larger d. The cells produced would get smaller and smaller.

d; the cells produced would get smaller and smaller, as they would not have sufficient time to double their mass before dividing.

Proteins are ______[[1]]________ built from amino acids, which each have an amino group and a ______[[2]]_______ group attached to the central _____[[3]]__________. There are twenty possible ______[[4]]_________ that differ in structure and are generally referred to as "R." In solutions of neutral pH, amino acids are ____[[5]]___________, carrying both a positive and negative charge. When a protein is made, amino acids are linked together through _____[[6]]__________, which are formed by condensation reactions between the carboxyl end of the last amino acid and the _______[[7]]____________ end of the next amino acid to be added to the growing chain.

polypeptides, carboxyl, a-carbon, side chains, ionized, peptide bonds, amino

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. 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 __________________.

proteins, amphipathic, lipid bilayer, fatty acid tails, hydrophilic head groups, phospholipids, sugars

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 the carbon-fixation process in chloroplasts, carbon dioxide is initially added to the sugar _______ __________. The final product of carbon fixation in chloroplasts is the three-carbon compound ________ _________. This is converted into ______________ (which can be used directly by the mitochondria), into_______________ (which is exported to other cells), and into _________ ________ (which is stored in the stroma). The carbon-fixation cycle requires energy in the form of_____ ____________ and reducing power in the form of ________________.

ribulose 1 5-biphosphate, glyceraldehyde 3-phosphate, pyruvate, sucrose, starch, ATP, NADPH

Whereas ionic bonds form a(n) ______[[1]]____________, covalent bonds between atoms form a(n) ______[[2]]___________. These covalent bonds have a characteristic bond ______[[3]]____________ and become stronger and more rigid when two pairs of electrons are shared in a(n) _____[[4]]_____________. Equal sharing of electrons yields a(n) _______[[5]]___________ 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 ______[[6]]____________ covalent bonds should not be confused with the weaker ______[[7]]____________ bonds that are critical for the three-dimensional structure of biological molecules and for interactions between these molecules.

salt, molecule, length, double bond, nonpolar, polar, noncovalent

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. The α helices and β sheets are examples of protein ______[[1]]____________ structure. A protein such as hemoglobin, which is composed of more than one protein _____[[2]]_____________, has _______[[3]]___________ structure. A protein's amino acid sequence is known as its _______[[4]]___________ structure. A protein_________[[5]]_________ is the modular unit from which many larger single-chain proteins are constructed. The three-dimensional conformation of a protein is its_____[[6]]_____________ structure

secondary, subunit, quaternary, primary, domain, tertiary

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. A newly synthesized protein generally folds up into a _______ __________conformation. All the information required to determine a protein's conformation is contained in its amino acid _______ ___________. On being heated, a protein molecule will become __________________ as a result of breakage of_________________ bonds. On removal of urea, an unfolded protein can become ________________. The final folded conformation adopted by a protein is that of ________________ energy.

stable, sequence, denatured, noncovalent, renatured, lowest

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