Cell Bio, EXAM 1 MEGA SET
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
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
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.
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 inner (plasma) membrane of E. coli is about 75% lipid and 25% protein by weight. How many molecules of membrane lipid are there for each molecule of protein? (Assume that the average protein is Mr 50,000 and the average lipid is 750.)
200
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
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
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.
A
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.
A
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.
A
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.
A
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
A
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.
A
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.
A
How do tRNAs become attached to the correct amino acid? A. aminoacyl-tRNA synthetases B. RNA polymerases C. rRNA ribozymes D. translation initiation factors
A
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
A
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
A
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
A
Long noncoding RNA (lncRNA) can function as a(n) A. protein scaffold. B. RNA polymerase. C.transcriptional regulator. D. telomerase.
A
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
A
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
A
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.
A
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.
A
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
A
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
A
The bonds that link two DNA strands together are A. hydrogen bonds. B. electrostatic interactions. C. phosphodiester bonds. D. phosphoanhydride bonds.
A
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
A
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.
A
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
A
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.
A
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.
A
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
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.
A
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%
A
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
A
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.
A
The sequence at which DNA replication begins tends to have which characteristic? A. AT-rich B. A-rich C. G-rich D. GC-rich
A
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.
A
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
A
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
A
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.
A
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.
A
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
A
What is the name of the DNA sequence where replication begins? A. replication origin B. initiator C. replication fork D. DNA template
A
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
A
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
A
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
A
What performs the function of bacterial sigma factor in eukaryotes? A. general transcription factors B. initiation proteins C. nucleosomes D. promoters
A
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
A
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
A
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.
histones & evolution
-are among the slowest evolving proteins known -5 out of 100 amino acids will change in a billion years of evolution
telomeres
-at each of the two ends of a chromosome -contains repeated nucleotide sequences required for the ends of chromosomes to be replicated -cap and protect end of chromosomes
how do base pairs stack?
-base pairs stack nearly flat and perpendicular to the backbone
both strands of DNA double helix must...
-carry COMPLEMENTARY patterns of hydrogen bond donors and acceptors
interphase chromosomes
-chromosomes during interphase -are decondensed, long, thin, threads of DNA in nucleus -not tangled b/c they occupy particular region of nucleus so different chromosomes wont become entangled (nucleolus) -specialized for expressing genes & replicating chromosomes
mitotic chromosomes
-chromosomes during mitosis -are very compact, condensed -specialized for the separation of sister chromatids and partition to daughter cells
each DNA strand/chain is ____
-composed of 4 types of nucleotide subunits -has two strands held together by hydrogen bonds between bases of nucleotides
backbone of DNA is composed of what? -what differs on each chain
-composed of nucleotides that are covalently linked together in a chain through sugars and phosphates -only base that differs so each polynucleotide chain in DNA can be seen as: sugar-phosphate backbone strung w/ 4 types of beads (A, C, G, T)
how are the nucleotides linked? And what does it form
-covalently linked together by phosphodiester bonds in a chain through the sugars and phosphates -this forms a backbone of alternating sugar-phosphate-sugar-phosphate
inversion
-cut DNA in 2 places, rotate 180 degrees and reconnect -type of genetic mutation -causes patchy eye color in flies
-regions of the chromosome that decondensed & condensed...
-decondensed (extended) = gene expression -condensed = non expressed genes
DNA
-discovered in 1940's that DNA carries genetic/hereditary information -long polymer composed of only 4 types of nucleotide subunits -are orientable polymers w/ a head (5') and tail (3')
genome size and chromosome size..
-do not correlate with the complexity of an organism -species that are closely related can have very different chromosome numbers & karyotypes
when do chromosomes rearrange?
-during evolutionary divergence
reverse complement
-each strand in a double stranded DNA is the reverse complement sequence of each other
nucleases
-enzymes that digests DNA by cutting phosphodiester bonds between nucleotides
linker DNA
-exposed double stranded DNA between nucleosome core particles -about 53 base pairs of linker DNA
purine
-fat 2 ring base -A & G
x chromosomes in females
-females contain 2 x chromosomes -double dose of x chromosome products is lethal so females can permanently inactivate 1 of the 2 x chromosomes in each cell -cells randomly inactivate either mother or father's X chromosome in early development by condensing it into heterochromatin -condensed & inactive state of that x chromosome will be inherited in the descendants of those cells
Avery Experiment
-followed up on Griffith's work -isolated the hereditary component biochemically and showed it was DNA -the transforming principle was DNA b/c it caused heritable change in bacteria that received it -conclusion: molecule that carries heritable information is DNA
heterochromatin's downfalls
-genes accidentally packaged into heterochromatin fail to be expressed, causing disease -can keep genes shut down or silenced
junk DNA
-genes in both strands contain non-coding DNA called junk DNA -may seem useless, but DNA itself acting as spacer material can be crucial for long term evolution and proper activity of genes -comparing genome sequences of many species show a part of this extra DNA is highly conserved (similar) showing it serves an important function
-how does eukaryotic replication go? -why?
-goes bidirectionally (in opposite directions) from multiple origins of replications -to ensure DNA molecules are replicated rapidly
a polynucleotide has a head and a tail called?
-head: 5' -> phosphate -tail: 3' -> hydroxyl
H1 linker histone
-histone that helps coils nucleosomes together into a 30 nm fiber -not part of the octomeric histones -forms a more condensed chromatin fiber
why are histones positively charged?
-histones are positively charged to neutralize the negative charge of the phosphates on the DNA backbone
octomeric histone core
-in each nucleosome core particle -contains 2 copies of each histones: H2A, H2B, H3, H4 -double stranded 147 bp DNA winds around the octomeric histone core
heterochromatin
-interphase chromatin -most highly condensed, gene poor region of chromosome -usually found near centromere and telomere -is associated with specific histone tail modification states (H3) -b/c of histone tail modification, heterochromatin spreads along chromosome until they're blocked w/ a barrier
where do eukaryotes pack their genomes
-into small nuclei
Griffiths experiment
-late 1920's -was studying pneumococcus, a bacteria that causes pneumonia -comes in 2 forms -pathogenic pneumococci injected (s strain): killed mouse -harmless form injected (r strain): mouse lived -pathogenic pneumococci killed by heating (s strain heated) injected: did not cause infection in mouse -heat killed pathogenic bacteria and live harmless bacteria injected (s strain heated + r strain): mouse died -animals died of pneumonia -heat killed pneumococci converted harmless bacteria into lethal form -conclusion: showed permanent inheritance of virus from dead bacteria -lead to Avery's experiment
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.
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.
A
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
A
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
A
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
A
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.
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
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
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
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
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.
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
The first living things on Earth probably generated ATP by what mechanism? A) fermentation B) oxidative phosphorylation C) photosynthesis D) carbon fixation
A) fermentation
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.
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.
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.
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
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
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
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
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
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.
B
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.
B
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.
B
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.
B
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
B
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.
B
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.
B
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.
B
The technique whereby human chromosomes are stained and identified is called a A. chromosome display. B. karyotype. C. genotype. D. phenotype.
B
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
B
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
B
What percentage of human genes have clearly recognizable homologs in the fruit fly? A. 10% B. 50% C. 99% D. 74%
B
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
B
When are chromosomes in their most compacted form? A. during interphase B. during mitosis C. during replication D. They are always equally compacted.
B
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.
B
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
B
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.
B
Which of the labels in the following figure shows a nucleosome core particle?
B
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
B
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
B
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.
B
___________ 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
B
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
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
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
Imagine that an RNA polymerase is transcribing a segment of DNA that contains the following sequence: (4 points) 5′-AGTCTAGGCACTGA-3′3′-TCAGATCCGTGACT-5′ a. If the polymerase is transcribing from this segment of DNA from left to right, which strand is the template? (circle either Top or Bottom).
Bottom
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.
C
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.
C
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
C
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
C
How do point mutations typically arise? A. chemical carcinogens B. radiation C. replication errors D. cell-division errors
C
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.
C
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.
C
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
C
Which type of RNA is converted into protein for performing its cellular function? A. tRNA B. rRNA C. mRNA D. miRNA
C
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.
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.
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.
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
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
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.
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
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
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.
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.
D
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.
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
How does the tRNA synthetase enzyme charge a tRNA with the correct amino acid?
Each different tRNA synthetase has one region that recognizes the tRNA anticodon and a second region that attaches the matching amino acid to the CCA at the 3' end of the tRNA. There are many aminoacyl-tRNA synthetases in the cell. Each one makes multiple contacts with the specific tRNA. One part of the enzyme recognizes the anticodon base triplet. A second region carries the matching amino acid that is added to the CCA at the 3' end of the tRNA.
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?
It provides information into where and when a gene is expressed.
Which of these statements about the composition of biological membranes is false?
In a given eukaryotic cell type (e.g., a hepatocyte), all intracellular membranes have essentially the same complement of lipids and proteins
What does cholesterol do to cell membranes?
In animal cells, membrane fluidity is modulated by the inclusion of the sterol cholesterol. This molecule is present in especially large amounts in the plasma membrane, where is constitutes about 20% of the lipids in the membrane by weight. Cholesterol molecules are short and rigid, so they fill the spaces between neighboring phospholipid molecules left by the kinks in their unsaturated hydrocarbon tails. So, cholesterol tends to stiffen the bilayer, making it less flexible, as well as less permeable.
Using the genetic code here, determine the amino acids that a polynucleotide of UC would code for.
Leu, Ser- A poly-UC molecule would be UCUCUCUCUCUC, and thus would have nonoverlapping triplets of UCU and CUC. Based on the genetic code, these triplets code for Ser (UCU) and Leu (CUC).
________ are the most abundant molecules in the animal cell membrane, whereas ________ make up 50% of the membrane by mass.
Lipids, proteins
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
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
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)
Different between mechanisms of DNA polymerase and RNA polymerase
DNA Polymerase: needs a based-paired 3' OH for polymerization rxn to occur RNA Polymerase can polymerize two nucleotides without a base paired 3' OH
(Q020) The rules of which fundamental process were elucidated in the bacterium Escherichia coli (E. coli)?
DNA Replication.
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.
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.
A.nerve terminal - 4 B.cell body - 1 C.axon - 3 D.dendrite - 2
Match the numbered lines in the diagram with the following structures: (4 points)
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.
At which site on the DNA of a gene does RNA polymerase release its newly made RNA?
Terminator- Signals in the nucleotide sequence of a gene tell RNA polymerase where to start and stop transcription. Transcription is initiated by the promoter region, which is not transcribed. Transcription is stopped at the terminator, which, unlike the promoter, is actually transcribed. The terminator sequence functions to stop transcription by causing RNA polymerase to release both the newly formed transcript and the DNA template.
Manufacturing of margarine:
The fats produced by plants are generally unsaturated and therefore liquid at room temperature, unlike animal fats such as butter or lard, which are generally saturated and therefore solid at room temperature. Margarine is made of hydrogenated vegetable oils their double bonds have been removed by the addition of hydrogen, so that they are more solid and buttermilk at room temperature.
1
The figure shows a ribose sugar. RNA bases are added to the part of the ribose sugar pointed to by arrow _____.
2
The figure shows a ribose sugar. The part of the ribose sugar that is different from the deoxyribose sugar used in DNA is pointed to by arrow ____.
3
The figure shows a ribose sugar. The part of the ribose sugar where a new ribonucleotide will attach in an RNA molecule is pointed to by arrow ____.
The fluidity of a cell membrane:
The fluidity of a cell membrane is the ease with which its lipid molecules move within the plane of the bilayer, this important function has to be maintained within certain limits.
What is the role of K+-gated ion channels in an action potential?
They help reverse the action potential by repolarizing the cell.
Which of the following is a difference between transporters and channels?
Transporters can facilitate both active or passive transport of solutes; channels facilitate only passive transport.
Determine whether the following statement is true or false: In isolation, the formation of an activated carrier, such as ATP, NADH, or NADPH, is an energetically unfavorable reaction.
True
Each eukaryotic chromosome must contain the following DNA sequence elements: one centromere, two telomeres, and multiple origins of replication.
True
Neurotransmitters are small molecules released into the synaptic cleft after the fusion of synaptic vesicles with the presynaptic membrane.
True
Unless specified otherwise, a nucleic acid sequence is always written in the 5' to 3' direction.
True
Determine whether the following statement is true or false: Some genes do not encode proteins but instead encode functional RNA.
True- Some genes do not encode proteins but instead encode functional RNA. Unlike mRNA, these functional RNAs are transcribed but are not used as a template for translation. These non-protein-coding RNAs include tRNA, rRNA, and miRNA and, like proteins, have various roles serving as regulatory, structural, and catalytic components of cells.
Determine whether the following statement is true or false: Once translation is complete, all of the proteins shown being synthesized in this image are expected to be identical.
True- The polyribosome is a series of ribosomes that can simultaneously translate the same mRNA molecule. All of the individual ribosomes are using the same mRNA, and therefore are all reading the same information, which will lead to the synthesis of identical proteins. The formation of polyribosomes greatly increases the efficiency of protein production from a single mRNA molecule.
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.
(Q021) Which method is used for separating proteins based on specific interactions with other molecules?
affinity chromatography
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.
What is the benefit of protein synthesis in polyribosomes?
More protein can be produced from a single RNA. Having more than one ribosome bound to a single mRNA allows many polypeptide chains to be synthesized simultaneously. This allows much more protein to be produced from one mRNA molecule than if each ribosome had to wait for the previous one to finish.
Part of the protein that is synthesized by a ribosome first
N-terminus
Which part of a protein is synthesized by a ribosome first?
N-terminus Remember that the covalent peptide bond that links amino acids into polymers involves the amino group of one amino acid and the carboxyl group of the other. Therefore, in any polypeptide, there will always be a free amino group at one end of the molecule and a free carboxyl group at the other. The nature of the peptidyl transferase activity of the ribosome is such that the amino group of the new amino acid being added reacts with the carboxyl group of the growing polypeptide. Therefore, the first amino acid in the polypeptide (that is, the one specified for by the first codon) will have its amino group remain free. This is referred to as the N-terminus. Additionally, because translation proceeds 5' to 3' along the mRNA molecule, the amino acids coded for at the 5' end of the transcript will be located at the N-terminus of the polypeptide.
(Q019) 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+
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+ FEEDBACK: Cells maintain high concentrations of NAD+ so that it is readily available to accept electrons from the oxidation of food molecules in catabolic reactions.
The C-terminal domain of _____ must be phosphorylated in order to activate the initiation complex of transcription.a. TFIID
RNA polymerase II
n eukaryotes there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a kinase protein?
RNA polymerase II
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.)
This large and complex general transcription factor complex has a DNA helicase activity that exposes the template for RNA polymerase II transcription. It also has a kinase activity that phosphorylates the C-terminal polymerase tail leading to promoter clearance. The specific protein that is responsible for the phosphorylation event is...
TFIIH
Not long ago, it was believed that a count of the number of protein-coding genes would provide a count of the number of proteins produced in any given eukaryotic species. This is incorrect, largely due to the discovery of widespread _____.
alternative splicing
(Q017) How does binding of GTP to a GTP-binding protein affect its activity?
always activates the protein
How does binding of GTP to a GTP-binding protein affect its activity?
always activates the protein
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.)
Proteins are composed of ____________ that contain a(n) ____________ group, an acid group, and a variable R group.
amino acids, amino
When two or more ____________ are bonded together, a ____________ is formed and when a chain of ____________ are bonded together, a ____________ is formed.
amino acids, peptide, amino acids, polypeptide
The sequence of ____________ greatly influence the behavior and function of the resulting ____________ .
amino acids, polypeptide
A sequence of ____________ strung together in a strand forms a ____________ structure.
amino acids, primary
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
How do tRNAs become attached to the correct amino acid?
aminoacyl-tRNA synthetases- Enzymes called aminoacyl-tRNA synthetases recognize tRNAs with a specific anticodon as well as the amino acid for that tRNA and catalyze a reaction to join them together. This is called "charging" a tRNA.
(Q005) The genes in the genome of an adult organism
are expressed or silenced depending on whether a gene is needed in that cell type and environment.
Peripheral membrane proteins:
are generally noncovalently bound to membrane lipids.
When/Where RNA capping of 5' end of transcript takes place
as RNA is being transcribed
Where or when does RNA capping at the 5' end of the transcript take place?
as an RNA is being transcribed
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
(Q024) A segment of DNA in the genome that is not a protein-coding gene
can be used to regulate gene activity.
(Q004) Mistakes in replicating the DNA of a cell before division
can have positive, negative, or neutral effects.
Mistakes in replicating the DNA of a cell before division
can have positive, negative, or neutral effects.
These groups are arranged around a central ____________ atom.
carbon
(Q018) All amino acids have which of the following chemical groups in common?
carboxyl group
All amino acids have which of the following chemical groups in common?
carboxyl group
Which chemical group is found on all amino acids?
carboxylic acid group
Which of the following carbohydrates would NOT be a molecule used for energy storage?
cellulose
Plants use a polysaccharide called ____________ for structural support. This molecule is comprised of ____________ molecules that are alternately flipped for increased support.
cellulose, glucose
Which of the following specialized DNA sequences provides an attachment point for the segregation of duplicated chromosomes?
centromeres
which of the following specialized DNA sequences provides an attachment point for the segregation of duplicated chromosomes?
centromeres
Animals and fungi use ____________ for structural support. It's found in the ____________ of insects and crustaceans and makes up fungal cell walls.
chitin, exoskeletons
Reactions that build larger molecules in the cell are called ___________; reactions that break down molecules into smaller ones are called ___________.
anabolic; catabolic FEEDBACK: Metabolism is the sum total reactions in a cell, which are of two types. Catabolic reactions are the reactions where cells break down the large molecules in foodstuffs into their constituent building blocks. Anabolic reactions are biosynthetic—they build larger molecules from smaller building blocks.
For the process of solute transport, the constant Kt is:
analogous to Km for an enzyme-catalyzed reaction.
These fats are produced mostly in ____________ .
animals
Some, including ____________ , function in defense by preventing antigens from destroying cells.
antibodies
Movement of water across membranes is facilitated by proteins called:
aquaporins
Steroids are composed of ____________ fused carbon ____________ .
four, rings
This means that in DNA, cytosine is always paired with ____________ , and adenine is always paired with ____________ .
guanine, thymine
Membrane proteins:
have all of the properties listed above.
Living systems can generate and maintain order without violating the second law of thermodynamics because they generate
heat FEEDBACK: Even though living systems produce ordered structures from smaller building blocks, this does not violate the second law of thermodynamics because they still create disorder by releasing energy in the form of heat. Heat is energy in its most disordered form.
(Q002) Living systems can generate and maintain order without violating the second law of thermodynamics because they generate
heat.
Some, such as ____________ , serve to transport molecules such as oxygen within the human body.
hemoglobin
(Q020) Biochemical subcompartments that form inside the nucleus are distinct from their immediate surroundings because of the
high concentrations of interacting proteins and RNA.
Some, such as ____________ , function in support and provide structure to ligaments, tendons, and skin.
collagen
The structure feature of DNA that hints at the mechanism for its replication is the
complementary base pairing
(Q013) Long polymers are made from single subunits in cells using a ___________ reaction, which ___________ water.
condensation; releases
Long polymers are made from single subunits in cells using a ___________ reaction, which ___________ water.
condensation; releases
Eukaryotic pre-mRNAs undergo a number of modifications such as capping at the 5' end. A 5' cap...
contains a triphosphate bridge between the terminal base (on the cap) and the 5' end of the pre-mRNA.
(Q016) How does phosphorylation of a protein affect its activity?
could increase or decrease activity
How does phosphorylation of a protein affect its activity?
could increase or decrease activity
(Q010) Disulfide bonds stabilize protein shape outside the cell by
covalent bonds between cysteines.
Disulfide bonds stabilize protein shape outside the cell by
covalent bonds between cysteines.
The action of a new drug is unknown, so you test various aspects of eukaryotic cell processes looking for an effect. You notice that the survival of cells exposed to this drug is very low. Further analysis shows that some proteins and mRNAs are much longer than they should be. One hypothesis is that the drug interferes with
either transcription termination signals or spliceosome activity
Which factors determine the force driving the passive transport of charged solutes across the membrane?
electrochemical gradient
What type of bonds are formed between histone proteins and DNA to form nucleosome core particles?
electrostatic interactions
Where are new phospholipids made?
endoplasmic reticulum
Which type of movement is the least common for lipids in a bilayer?
flip-flop
The type of motion least common in biological membranes is:
flip-flop diffusion of phospholipid from one monolayer to the other.
(Q007) Which of the following microscopy techniques allows the observation of living cells (i.e., NOT fixed cells)?
fluorescence microscopy
(Q012) The inner membrane of the mitochondrion appears ___________ because it provides___________.
folded; a large surface area for staging energy production processes
(Q014) Which of the following is a role that sugars can play outside of their role in energy production and storage?
formation of support structures
This type of reaction involves the ____________ of water as ____________ are linked together and ____________ built.
formation, monomers, polymers
(Q013) For the following uncatalyzed reaction at equilibrium, how would the reaction change if it was now an enzyme-catalyzed reaction at equilibrium?
forward reaction A would increase\ FEEDBACK: Enzymes lower the activation energy for reactions and thus increase the probability that the energy barrier can be surpassed for the reaction to proceed. They do not change the equilibrium point (the relative levels of reactants and product at equilibrium).
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
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
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
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
loss of 1
Enzymes increase the speed of a chemical reaction because they
lower of activation energy needed to start the reaction. FEEDBACK: Enzymes work by lowering the threshold energy input, called the activation energy, needed to start a reaction.
(Q008) Enzymes increase the speed of a chemical reaction because they
lower the activation energy needed to start the reaction.
Type of RNA converted into protein for performing its cellular fxn
mRNA
Which type of RNA is converted into protein for performing its cellular function?
mRNA
Which type of RNA is converted into protein for performing its cellular function?
mRNA- There are many different types of RNA that perform functions as RNA in the cell and are never translated into protein. These include tRNA, rRNA, and miRNA. The only RNAs that code for proteins are mRNAs.
MicroRNAs block the expression of a specific gene product by binding to the ___________ and inhibiting ___________.
mRNA; translation
Translated after they are exported from the nucleus
mRNAs
To make the coding strand of a DNA molecule into RNA, what would you do?
make the T's U's
(Q021) The fruit fly, Drosophila melanogaster (D. melanogaster) is an excellent model for studying fundamentals of development because
many of the genes involved in the development of the fruit fly are also found in humans.
The fruit fly, Drosophila melanogaster (D. melanogaster) is an excellent model for studying fundamentals of development because
many of the genes involved in the development of the fruit fly are also found in humans.
A binding site on the surface of a protein interacts specifically with another protein through
many weak non covalent interactions
(Q024) Strong and specific associations between macromolecules or between an enzyme and its substrate are due to
many weak noncovalent bonds.
Strong and specific associations between macromolecules or between an enzyme and its substrate are due to
many weak noncovalent bonds.
(Q009) A binding site on the surface of a protein interacts specifically with another protein through
many weak noncovalent interactions.
It is a ____________ that is comprised of adenine, ribose, and ____________ phosphate molecules.
nucleotide, three
Nucleic acids are made of ____________ , each of which contain 3 parts.
nucleotides
Pre-mRNAs must be capped, polyadenylated, and spliced in the _____________ before they can be _________________.
nucleus; exported
In plants, ____________ provide vital long-term energy storage.
oils
How many aminoacyl-tRNA synthetases most organisms have
one for each amino acid
How many different aminoacyl-tRNA synthetases do most organisms have?
one for each amino acid
Bacteria use ____________ for structural support within their cell walls.
peptiodoglycan
Proteins that are associated with the membrane by noncovalent interactions with other membrane proteins are called ___________ proteins.
peripheral membrane
(Q014) Lysosomes and peroxisomes both perform a series of reactions to break down molecules, but one difference between them is that
peroxisomes contain hydrogen peroxide.
(Q022) A readily available source of energy that cells use to drive reactions is stored in the ___________ bond.
phosphoanhydride
A readily available source of energy that cells use to drive reactions is stored in the ___________ bond.
phosphoanhydride
The type of bond that holds together neighboring subunits in a single strand of DNA is a
phosphoanhydride bond.
RNA polymerases join nucleotides through what kind of bond
phosphodiester
RNA polymerases join nucleotides through what kind of bond?
phosphodiester
(Q015) 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?
phospholipid
What kind of lipid molecule is represented in this figure?
phospholipid
Within all organisms, ____________ comprise the bulk of the plasma membrane, allowing it the many properties that it needs to function.
phospholipids
These oils are produced mostly in ____________ .
plants
Its function in the ____________ is to provide both flexibility and stability. Some steroids also function in cell to cell communication.
plasma membrane
The ____________ is composed of a phospholipid bilayer that is ____________ in nature.
plasma membrane, fluid
Carbohydrates exist as either monomers or ____________ , long chains of monomers bonded together.
polymers
Large biomolecules, or ____________ , are comprised of smaller subunits called ____________ .
polymers, monomers
Groups of three or more monomers are called ____________ and include ____________ and other molecules typically used for ____________ and structural support.
polysaccharides, starch, short-term storage
The figure below depicts which of the following mechanisms that cells use to maintain their identity through cell divisions?
positive feedback
The control of a gene product's levels or activity after transcription has taken place is called
post-transcriptional control.
A hydropathy plot is used to:
predict whether a given protein sequence contains membrane-spanning segments.
When two or more polypeptides bond together into a working protein, it represents a ____________ structure.
quatemary
(Q007) Which of the following levels of protein structure involves the interaction of more than one polypeptide chain into a three-dimensional structure?
quaternary
Which of the following levels of protein structure involves the interaction of more than one polypeptide chain into a three-dimensional structure?
quaternary
The sigma subunit of bacterial RNA polymerase ___________________.
recognizes promoter sites in the DNA.
Describes how eukaryotic activator proteins can regulate chromatin packaging to enhance transcription
recruiting chromatin-remodeling complexes to eject or slide nearby nucleosomes
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
(Q005) In an enzymatic reaction, a molecule gains an electron. This is known as a(n) ___________ reaction.
reduction
In an enzymatic reaction, a molecule gains an electron. This is known as a(n) ___________ reaction.
reduction FEEDBACK: Gain of electrons by a molecule is called reduction; loss of electrons is called oxidation.
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.)
These bonds have a ____________ energy associated with them, so when they break, energy is ____________ and ____________ is formed.
high, released, adenosine diphosphate
If a gene sequence in one organism is highly similar to the sequence of another gene in another organism it is called
homologous.
Some proteins, such as ____________ , function as chemical messengers and help regulate cell behavior.
hormones
(Q011) The main function of the nucleus is to
house the DNA in a separate cell compartment.
(Q001) Which type of noncovalent interaction can involve either the polypeptide backbone or amino acid side chains?
hydrogen bonds
Recognizes stop codons in mRNA
release factor
What recognizes the stop codons in an mRNA?
release factor
What recognizes the stop codons in an mRNA?
release factor- When the ribosome encounters a stop codon, instead of a tRNA binding, a protein called release factor binds and catalyzes the addition of a water molecule to the carboxyl end of the polypeptide and releases it.
Which type of noncovalent interaction can involve either the polypeptide backbone or amino acid side chains?
hydrogen bonds
Biomolecules are broken down into their subunits through ____________ reactions.
hydrolysis
Phospholipids have ____________ heads and ____________ tails.
hydrophillic, hydrophobic
(Q010) Which of the following occurs by bringing nonpolar surfaces together to exclude water?
hydrophobic forces
Phospholipids assemble into in a membrane using
hydrophobic forces
Which of the following occurs by bringing non polar surfaces together to exclude water?
hydrophobic forces
If one end of a DNA strand has a phosphate group on it, the chemical group on the other end must be
hydroxyl
For a neuron with an initial membrane potential at -70 mV, an increase in the movement of potassium ions out of that neuron's cytoplasm would result in the _____.
hyperpolarization of the neuron
(Q023) Covalent bonds in macromolecules are primarily important for
linking together monomers.
Covalent bonds in macromolecules are primarily important for
linking together monomers.
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.)
Oils, such as canola oil, are ____________ at room temperature because they contain primarily ____________ fatty acids.
liquids, unsaturated
These examples of polysaccharides function well as storage molecules since they are large and ____________ in water, which prevents them from passing through the plasma membrane. But storage is not the only function suited to polysaccharides.
insoluble
Lipids are ____________ in water due to the ____________ nature of their long hydrocarbon chains.
insoluble, nonpolar
Does not increase stability of eukaryotic mRNAs
intron
In eukaryotes, which parts of a gene are transcribed into RNA?
introns and exons
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
The reading frame to use for translating an mRNA into functional protein is determined by the
location of an AUG.
The tryptophan operon encodes the genes needed to synthesize tryptophan in bacterial cells. What happens when the concentration of tryptophan inside a cell is high
it activates the tryptophan repressor, which shuts expression of the tryptophan operon
How does methylation of histone tails affect the accessibility of DNA?
it can have different effects depending on the location
RNA in cells differs from DNA in that ___________________.
it contains the base uracil, which pairs with cytosine.
which of the following is a function of the protein component of chromosomes?
it packages the DNA strands
Reason why RNA molecule can be folded into a three dimensional shape
it's single stranded
(Q008) The defining property that differentiates prokaryotic cells from eukaryotic cells is their
lack of a nucleus
Catalytic sites for peptide bond formation during translation is found in this part of the ribosome
large subunit RNAs
The catalytic sites for peptide bond formation during translation is found in which part of the ribosome?
large subunit RNAs
The catalytic sites for peptide bond formation during translation is found in which part of the ribosome?
large subunit RNAs- The catalysis of the peptide bonds in the growing polypeptide chain during translation is performed by the rRNA of the large subunit. The ribosome is a ribozyme; proteins play a largely structural role.
The reading frame to use for translating an mRNA into functional protein is determined by the
location of an AUG. The translation of an mRNA in eukaryotes begins when the initiator tRNA encounters the first AUG in an mRNA. The complex containing the initiator tRNA starts scanning the mRNA from the 5' end to find the AUG.
A cell membrane made up primarily of lipids with which characteristics would be the least fluid (i.e., most stiff)?
long, saturated fatty acid tails
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
Modern macromolecules that may be relics of hypothesized RNA world
ribosome spliceosome
An RNA message is decoded by which of the following?
ribosomes
Decodes RNA message
ribosomes
Term for an RNA molecule that possess catalytic activity
ribozyme
What is the best term for an RNA molecule that possesses catalytic activity?
ribozyme
What are two types of noncoding regulatory RNAs?
siRNAs and miRNAs
(Q018) 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.
side chains
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.
side chains
Name of the subunit of bacterial RNA polymerase that recognizes the promotor of a gene
sigma factor
What is the name of the subunit of bacterial RNA polymerase that recognizes the promoter of a gene?
sigma factor
Bacterial mRNAs are transcribed and translated
simultaneously
Cells, compared with the extracellular fluid are
slightly negatively charged
Remove introns from an RNA transcript in the nucleus
snRNPs
Fats, such as lard, are ____________ at room temperature because they contain primarily ____________ fatty acids.
solids, saturated
For instance, plants use ____________ as a way to store glucose, either in its ____________ called amylose, or its ____________ , called amylopectin.
starch, unbranched form, branched form
Embedded within the plasma membrane are ____________ , which provide cell to cell communication and contribute to plasma membrane flexibility.
steroids
(Q013) One piece of evidence indicating that chloroplasts evolved from engulfed photosynthetic bacteria is
that they contain their own DNA.
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
Assembly of general transcription factors at a eukaryotic promoter begins at
the TATA box
The assembly of general transcription factors at a eukaryotic promoter typically begins at what site?
the TATA box
(Q016) The cell components that move materials from one organelle to another are called
transport vesicles.
Plasma membrane proteins that move ions in and out of cells using active transport are called
transporters
An electrogenic Na+ transporter:
transports Na+ without concurrent transport of any other charged species
Determine whether the following statement is true or false: In bacteria, most protein-coding genes lack introns.
true
T or F in bacteria most protein coding genes lack introns
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.)
(Q014) The function of feedback inhibition of an enzymatic pathway is to
turn off synthesis of a product when it is in abundance.
The structure of a proteasome is shown below. What group is recognized by region A to indicate that the protein is marked to be eliminated?
ubiquitin
(Q025) The technique that scientists used to determine that hemoglobin was a single large macromolecule rather than a loose conglomeration of small organic molecules was
ultracentrifugation
The technique that scientists used to determine that hemoglobin was a single large macromolecule rather than a loose conglomeration of small organic molecules was
ultracentrifugation
(Q020) Condensation reactions are energetically ___________ and hydrolysis reactions are energetically ___________.
unfavorable; favorable
Condensation reactions are energetically ___________ and hydrolysis reactions are energetically ___________
unfavorable; favorable FEEDBACK: Condensation reactions reduce the disorder in the universe and are energetically unfavorable. Hydrolysis reactions increase the disorder in the universe and are energetically favorable.
(Q017) The following image shows two triacylglycerol molecules with different fatty acid chains. If these fatty acids were in a phospholipid molecule, which of the two would form the most fluid membrane?
unsaturated
The following image shows two triacylglycerol molecules with different fatty acid chains. If these fatty acids were in a phospholipid molecule, which of the two would form the most fluid membrane?
unsaturated
What is the value of ΔG at equilibrium?
zero FEEDBACK: When equilibrium is reached, the forward and reverse reactions are equal, so there is no net change in the number of reactants and products. The reaction does not proceed forward or backward at this point and ΔG is equal to zero.
When are chromosomes in their most compacted form?
during mitosis
Benefit of protein synthesis in polyribosomes
more protein can be produced from a single RNA
Which of the following is a cell type in humans that uses voltage-gated ion channels?
muscle cells
(Q001) The function of a(n) _________ cell, which has a long, branched structure, requires many connections to be made with neighboring cells.
nerve
The ____________ bases of one strand exhibit ____________ with the bases of other strands.
nitrogen, complementary base pairing
Do some codons have to code for an animo acid in mRNA molecules
no
In mRNA do some codons code for more than one amino acid
no
At the beginning of this century there was a general announcement regarding the sequencing of the human genome and the genomes of many other multicellular eukaryotes. Many people were surprised that the number of protein-coding sequences was much smaller than they had expected. Which of the following could account for much of the DNA that is not coding for proteins?
non-protein-coding DNA that is transcribed into several kinds of small RNAs with biological function
If the products of a reaction have more free energy than the reactants, then that reaction is
not energetically favorable FEEDBACK: Reactions that have products with LESS free energy than the reactants will release free energy and create more disorder in the system. These will proceed spontaneously and are energetically favorable. However, when products of a reaction have MORE free energy than the reactants, there is no release of energy, and the reaction is not energetically favorable.
(Q009) If the products of a reaction have more free energy than the reactants, then that reaction is
not energetically favorable.
The process of gene expression always involves which process(es) described in the central dogma?
transcription
Which type of lipids are the most abundant in the plasma membrane? (a) phospholipids (b) glycolipids (c) sterols (d) triacylglycerides
(a)
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)
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)
how are nucleosomes packed?
-they are packed and coiled on top of one another to generate a more compact structure
genome
-total complement of DNA sequence in an individual
right handed helix
-two DNA strands wind around each other to form a right handed helix w/ 10 bases per turn
bacteriophage
-used in Hershey-Chase Experiment -virus that infects and kills bacterium E. coli -injects its genetic information into bacterial host cell which transforms bacteria into virus producing factory -only contains DNA and protein
what are most RNA molecules encoded by genes used for?
-used to produce a protein
when do proteins evolve more quickly?
-when more different sequences are compatable with their function
origin of replication
-where replication of DNA begins -eukaryotic chromosomes contain many origins
Using the genetic code below, determine the amino acids that a polynucleotide of UC would code for.
. Leu, Ser
(Q002) A folded protein structure with which free-energy (G) value would likely have the most stable conformation?
1
Which of the following is the main point of control for regulating gene expression levels?
transcription
Part of mRNA molecule ribosomal subunits first bind
5' end
Increase stability of eukaryotic mRNAs
5' end cap and poly A tail
All nucleic acid (even RNA) is polymerized in the ______ direction.
5'-3'
The splicing of introns out of an mRNA molecule is catalyzed by
RNA molecules that base pair with the splice to promote intron removal
Which of the following does not occur before a eukaryotic mRNA is exported from the nucleus?
The ribosome binds to the mRNA.
In bacteria, both RNA and DNA polymerase only in one direction along the template strand, synthesizing the growing nucleotide strand in the _____ direction
5'-3'
Export of RNA from the nucleus requires the RNA to have which characteristic(s)?
5′ cap and poly-A tail
b. What will be the sequence of that RNA (be sure to label the 5′ and 3′ ends of your RNA molecule)?
5′-AGUCUAGGCACUGA-3′
(Q023) What is a protein family?
a structurally related group of proteins
What is a protein family?
a structurally related group of proteins
The technique whereby human chromosomes are stained and identified is called a
Karyotype
This type of reaction involves the ____________ of water as polymers are broken down into monomers.
addition
ATP, or ____________ provides energy for nerve impulse conduction, muscle contraction, and many other chemical reactions necessary for life.
adenosine triphosphate
Structure responsible for selecting and transporting only properly processed eukaryotic mRNAs into the cytoplasm
nuclear core complex
What structure is responsible for selecting and transporting only properly processed eukaryotic mRNAs into the cytoplasm?
nuclear pore complex
Which of these macromolecules is NOT commonly found in the plasma membrane?
nucleic acids
Step of gene expression when cells can amplify the number of copies of a protein made from a single gene
transcription and translation
nucleosome core particles
-DNA wound around a core of 8 histone proteins -each core has this octomeric histone core
what were DNA and protein radioactively labeled w/ in hershey-chase experiment?
-DNA: 32 P -Protein: 35 S
Must bind to the promoter to allow RNA polymerase to bind and begin transcription
transcription factors
Based on the figure, which of these statements is/are correct?
-For different genes, opposite strands of DNA can serve as a template. -RNA is always polymerized in the 5'-to-3' direction.
what are the 4 types of histones that make up a octomeric histone core?
-H2A -H2B -H3 -H4
-what does complementary base pairing allow? -what is significant about the width?
-allows base pairs to be packed in energetically most favorable way on the inside of the double helix -each base pair has similar width thus the sugar-phosphate backbones are held at equal distance
position mutants
-the expression of genes change when they get moved near heterochromatic regions ex) normal gene for white eyes for flies get moved towards heterochromatic region -> that gene is turned off -> results in red eye color
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)
Which of the following phospholipid precursors is the most hydrophobic? (a) triacylglycerol (b) diacylglycerol (c) phosphate (d) glycerol
(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)
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)
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.
Membranes undergo spontaneous rearrangement if torn. Which of the following would happen if a cell membrane had a large tear? Figure 11-17
(c) vesicles form
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)
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)
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
since the sequence of one strand of DNA is read from 5' to 3', the reverse complement of a sequence is..
-the sequence of its paired (or second) strand
every DNA base pair has..
-1 purine (A or G) and 1 pyrimidine (C or T)
in a double helix, how many base pairs are there per helical turn? -how long per unit turn?
-10 -3.4 nm per unit turn
how many base pairs of DNA wind around a octomeric histone core?
-147 base pairs of double helix DNA
biologists during ____ had difficult time accepting _____ b/c____
-1940's -DNA as the genetic material -b/c DNA is so simple in chemistry
until the ____, scientists believed that ____ carried/mediated heredity because...
-1950's (Watson & Crick) -scientists thought proteins mediated heredity instead of DNA -this is because proteins are more diverse than DNA -discovered that it was really DNA
Hershey-Chase Experiment
-1952 -used bacteriophage to study bacterial transformation -bacteriophage injects their genetic material (protein or DNA?) into the bacterial host cell -this transforms bacteria into virus producing factory
-DNA double helix are ____ and are held together by____? -What is on the inside of the double helix?
-2 antiparallel polynucleotide chains held together by hydrogen bonding between bases on different strands -bases are on the inside of double helix -sugar-phosphate backbones are on outside of double helix
human cells contain how many copies of each chromosome?
-2 copies of each chromosome: 1 from mom & 1 from dad -this does not include germ cells (sperm and eggs)
how long is all the DNA in a human cell if laid out from end to end?
-2 meters
what is the width of the backbone of double stranded DNA?
-2 nm
Even though DNA of interphase chromosomes are..
-20 times less condensed than mitotic chromosomes, they are still packed tightly -there is a 500 fold compaction over totally uncompacted DNA
the nucleotides in DNA are composed of..
-5 carbon sugar: deoxyribose -phosphate -nitrogenous base; which can be either: adenine (A), cytosine (C), guanine (G), thymine (T)
how do bases pair? how many bonds are between them
-A pairs w/ T : 2 bonds -G pairs w/ C : 3 bonds -in each case, a fat purine (A & G) pairs with a skinny pyrimidine (C & T)
how is the sequence of one strand of DNA read?
-ALWAYS from 5' to 3'
-what is the complement of GTAACGGTCA? -the reverse complement?
-CATTGCCAGT -TGACCGTTAC
Translation proceeds in a series of steps in the active site of the ribosome. Which of the following are important steps in polypeptide formation?
-The RNA in the P site makes hydrogen bonds with the 3' end of the aminoacyl-tRNA. -The hydrogen bonds formed between ribosomal RNA and tRNAs position the aminoacyl-tRNAs to catalyze peptide bond formation. The P site ribosomal RNA base-pairs with the 3' end of the tRNA holding the growing polypeptide, helping to position it in the correct orientation. The incoming aminoacyl-tRNA also forms hydrogen bonds, not covalent bonds, with the ribosomal RNA in the A site. The hydrogen bonds formed between ribosomal RNA and the tRNAs in the A and P sites help position the amino acids to catalyze peptide bonds formation. After peptide bond formation, the ribosome changes conformation and the empty tRNA in the P site is released. The tRNA holding the growing polypeptide is transferred from the A site to the P site and a new tRNA enters the A site of the ribosome.
who discovered the structure of DNA and when?
-Watson & Crick -1953
what linkage gives each polynucleotide strand a chemical polarity?
-a free monophosphate group on each 5' end -a unlinked hydroxyl group on 3' end -b/c 2 ends are chemically different
histone tails
-all histones in octamer have long positively charged tail sticking out from each nucleosome core -are covalently modified to allow for control over structure and function of the chromosome
histone tails & modifications
-all tails on core histones are reversibly covalently modified -these covalent modifications are a histone code (chemical signals) that affect condensation of the chromosome and the binding of proteins to chromatin -histone modification can spread like a wave along chromatin due to modification specific proteins
which amino acids are likely to occur frequently in histones to neutralize the charge of DNA backbone?
-lysine and arginine
nucleosomal core particle
-made up of DNA and a histone protein
homologous chromosomes
-maternal and paternal chromosomes -everything but sex chromosomes
chromosome
-means colored body b/c they easily absorbed staining dyes -often stained blue w/ dye DAPI -discovered during 1900's as threadlike structures in nucleus -contains DNA & proteins -carries genes -are condensed in dividing cells -are loose and diffuse in non-dividing cells -10 microns
does DNA always have to be double stranded?
-no, DNA can be single stranded
nuclease attack
-nuclease digests unprotected linker DNA allowing core particles to be isolated -DNA wound around nucleosome is protected
beads on a string
-nucleosome core particles interspread by linker DNA -string: DNA -beads: nucleosome core particle -11 nm
minor groove
-occurs where the backbones are close together
major groove
-occurs where the backbones are far apart -more space -proteins typically bind here b/c of larger angle -all 4 base pairs can be distinguished here, but not minor groove
Giemsa Staining
-old fashioned way to identify chromosomes for A+T base content -dyes produce predictable pattern of bands along each type of chromosome
karyotype
-ordered display of all chromosomes from a species or individual -can detect diseases caused by chromosomal abnormalities ex) if parts of a chromosome are lost, or switched between chromosomes
base pair
-pair between a fat purine and skinny pyrimidine
epigenetic inheritance
-parental modified histones are distributed randomly to daughter chromosome ... no equal -remainder of daughter DNA gets new, not yet modified histones -proteins recognize these sites and modify them to re-establish parental pattern of histone modification -inheritance outside DNA, doesn't alter its sequence
proteins and their functions
-perform most of cell's functions -serve as building blocks for cell structures -form enzymes that catalyze the cell's chemical reactions -regulate activity of genes -enable cells to move and communicate w/ each other
centromeres
-point of attachment of mitotic spindle & sister chromatids -binds sister chromatids and allows for equal separation to daughter cell by attaching them to the mitotic spindle
histones
-positively charged proteins that bind to negatively charged DNA backbone -help package and order DNA into structural units called nucleosome: DNA winds twice around 8 histones -keeps DNA from tangling
chromatin remodeling complexes
-protein machines that decondenses interphase chromatin to allow access to DNA for expression and replication -requires ATP
chromatin
-protein with nuclear DNA -in 30 nm form; can be unfolded to beads on a string
how did Hershey & Chase determine if DNA or protein was the genetic material injected to transform bacteria?
-radioactively labeled protein (35 S) in one batch of virus and the DNA (32 P) in another -followed radioactivity to see if DNA or protein wound up inside bacteria -labeled protein/DNA -> virus infected e coli -> virus head sheared off surface of bacteria (which contained protein) -> centrifuged -> infected bacteria contained 32 P not 35 S -discovered DNA entered bacterial cell while proteins remained outside w/ empty virus heads -also found radioactive DNA was incorporated into next generation of virus -concluded that DNA enter bacterial host cells, not protein -genetic material has to be made of DNA
chromosome condesation
-reorganization of the long thin chromatin strands into compact chromosomes -varies over the cell cycle
euchromatin
-rest of interphase chromatin -decondensed, more accessible for gene expression
what is the most common form of DNA helix?
-right handed helix
genes
-segment of DNA that contains instructions for making a particular protein or RNA molecule -units of functional DNA that express proteins or RNA -are oriented: are located in 1 DNA strand or the other -are carried in chromosomes
what is the function of the protein components of chromosomes?
-serves to package and control the long DNA molecules
chromosome packing on multiple levels
-short region of DNA double helix: 2 nm -beads on a string form of chromatin: 11 nm -chromatin packed into nucleosomes: 30 nm -chromatin folded to loops: 700 nm -full chromosome: 1400
pyrimadine
-skinny single ring base -C & T
nucleolus
-specialized region in nucleus where ribosomes are synthesized -non coding DNA synthesized here?
antiparallel
-strands of DNA that are oriented in opposite directions (antiparallel) -why base pairs of 2 strands can fit and pair together w/in a double helix
pneumococcus
-studied in Griffiths experiment -a bacteria that causes pneumonia -comes in 2 forms: 1) a rough (pathogenic) form that causes lethal infection when injected 2) a smooth (harmless) form that can be conquered by animal's immune system... does not produce infection
nucleosome
-subunit of chromatin -composed of short length DNA wrapped around a core of 8 histone proteins -technically is a nucleosome core particle with one stretch of linker DNA -includes 200 nucleotide pairs of DNA
chromosome painting
-technique used to identify chromosomes -uses fluorescent in site hybridization (FISH) to uniquely label all chromosomes -steps: 1) isolate 1 chromosome 2) generate many single stranded DNA unique to that chromosome 3) label probes w/ unique fluorescent dye 4) hybridize probes to chromosomes: probes will specifically bring fluorescent dye to only 1 chromosome
base pairs can fit together w/in a double helix b/c...
-the 2 strands of the helix run antiparallel to each other ... they are oriented w/ opposite polarities
-major and minor grooves derive from... -when are the angles the same
-the angle of attachment of the base pairs to the backbones -at less than 180 degrees, the angles are the same for both G:C and A:T base pairs
The action potential is a wave of __1________________ that spreads rapidly along the neuronal plasma membrane. This wave is triggered by a local change in the membrane potential to a value that is _2________________ negative than the resting membrane potential. The action potential is propagated by the opening of _____3_____________-gated channels. During an action potential, the membrane potential changes from _____4_____________ to ____5______________. The action potential travels along the neuron's ____6______________ to the nerve terminals. Neurons chiefly receive signals at their highly branched ____7______________.
1) depolarization 2) less 3) voltage 4) negative 5) positive 6) axon 7)dendrites
What distinguishes the chemistry of life from other types of chemistry?
1. It takes place almost exclusively in water. 2. It is dominated by collections of polymers.
(Q004) 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?
18
Shown below is the logo of the DNA binding site for a transcriptional regulator. Which two positions are most important for the sequence specificity of the transcription factor?
2 and 3.
The shortest α helix segment in a protein that will span a membrane bilayer has about _____ amino acid residues.
20
A primary transcript (immature, non-processed) single-stranded RNA molecule has the following nucleotide composition: 30% A, 20% G, 24% C, and 26% U. What is the nucleotide composition of the double-stranded DNA molecule from which it was transcribed?
28% A, 22% G, 22% C, and 28% T DNA contains the bases adenine (A), thymine (T), guanine (G), and cytosine (C). On the other hand, RNA contains A, G, C, and uracil (U). Because the DNA molecule is double-stranded, the nucleotide composition of both strands must be taken into account when compared to the single-stranded nature of RNA. The template DNA strand that encodes this RNA molecule would contain: 30% T, 20% C, 24% G, and 26% A. The nontemplate strand, sometimes called the "sense strand" of the DNA, which is complementary to the template strand, would contain: 30% A, 20% G, 24% C, and 26% T. The double helix would thus contain an average of these values: 28% A, 22% G, 22% C, and 28% T.
Number of nucleotides necessary to specify a single amino acid
3
Number of reading frames in an RNA molecule that can potentially be translated into protein
3
Refer to the following graph of an action potential to answer the question below. The cell is not hyperpolarized; however, repolarization is in progress, as the sodium channels are closing or closed, and many potassium channels have opened at label _____.
3
In one catalytic cycle, the Na+/K+ ATPase transporter transports:
3 Na+ out, 2 K+ in, and converts 1 ATP to ADP + Pi.
RNA polymerase will move away from the promoter using the promoter-dictated directionality and uses what strand as a template to make a new RNA in the opposite direction
3'-5'
(Q005) How many bonds are made by a carbon atom?
4
How many bonds are made by a carbon atom?
4
Export of RNA from nucleus requires
5' cap and poly A tail
Export of RNA from the nucleus requires the RNA to have which characteristic(s)?
5' cap and poly-A tail
Name three covalent modifications that can be made to an RNA molecule in eukaryotic cells before the RNA molecule becomes a mature mRNA.
5' capping Polyadenylation Splicing
The sequence of the template strand of a DNA molecule is 5'-ACTGGCAATG-3'. What is the sequence of the RNA transcribed from this DNA?
5'-CAUUGCCAGU-3'- One of the major chemical differences between DNA and RNA is the presence of thymine (not uracil) in DNA and the presence of uracil (not thymine) in RNA. If the sequence of the template strand of a DNA molecule is 5'-ACTGGCAATG-3', then 5'-CAUUGCCAGU-3' must be the sequence of the RNA transcribed from this DNA. Transcription generates an antiparallel and complementary strand of nucleic acid. When a single-stranded nucleic acid sequence is written out, it is conventional to write the sequence in the 5'-to-3' direction. Therefore, 5'-CAUUGCCAGU-3' RNA is complementary to 5'-ACTGGCAATG-3' DNA.
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 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' One of the major chemical differences between DNA and RNA is the presence of thymine (not uracil) in DNA and the presence of uracil (not thymine) in RNA. If 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', then the sequence of the RNA made from this DNA would be 5'-CGGAUGCUUA-3'. Transcription generates an antiparallel and complementary strand of nucleic acid. When a single-stranded nucleic acid sequence is written out, it is convention to write the sequence in the 5'-to-3' direction. Therefore, 5'-CGGAUGCUUA-3' RNA is complementary to 5'-CGGATGCTTA-3' DNA. Review the figure below to help you keep track of coding versus template strands of DNA and how RNA is related to each.
The sequence of a region of DNA around the 5′ end of a gene in Escherichia coli is shown below. The -10 box and the transcription start site are (bolded and underlined). What would be the sequence of the first 10 nucleotides of the mRNA transcribed from this gene? Write down the sequence from 5′ to 3′ being sure to label each end. (5 points) 5′...GCGCTTGG(TATAAT)CGCTGGGGGTCAAAGAT...3′
5'-GGUCAAAGAU-3'
An RNA chain elongates in what direction?
5'-to-3' only- Like the DNA polymerase that carries out DNA replication, RNA polymerases catalyze the formation of the phosphodiester bonds that link the nucleotides together and form the sugar-phosphate backbone of the RNA chain. Therefore, the RNA strand elongates in the 5' to 3' direction only. This is because to add a nucleotide, there must be an available 3' hydroxyl group for the incoming nucleotide triphosphate to react with. Once this reaction takes place, a phosphodiester bond is established between the neighboring nucleotides, and the nucleic acid chain has grown by one nucleotide in length.
They contain a ____________ sugar, a ____________ group, and a ____________ base.
5-carbon, phosphate, nitrogen
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
A
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.
A
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
A
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
A
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.
A
How does an action potential spread along the cell membrane?
A change in membrane potential triggers the opening of nearby voltage-gated sodium channels in a one-way direction.
_______ is a sequence of DNA that contains the information required for making a particular functional RNA or protein
A gene
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
Which of these statements is generally true of integral membrane proteins?
A hydropathy plot reveals one or more regions with a high hydropathy index.
Structure of the plasma membrane plasma membrane:
A living cell is a self-reproducing system of molecules held inside a container, this container is the plasma membrane. Which is a two-ply sheet of lipid molecules, that is a fatty film so thin that it cannot be seen with a high microscope, into which proteins have been inserted. Every cell on Earth uses such a membrane to separate and protect its chemical components from the outside environment. Without membranes there would be no cell, and thus no life.
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
At what site do all charged tRNAs (with the exception of the initiator tRNA) first bind on the ribosome?
A site
Site all charged tRNAs except the intiator tRNA, first bind on the ribosome
A site
At what site do all charged tRNAs (with the exception of the initiator tRNA) first bind on the ribosome?
A site- In addition to a binding site for an mRNA molecule, each ribosome contains three binding sites for tRNA molecules, called the A site, the P site, and the E site. All charged tRNAs (with the exception of the initiator tRNA) first bind on the ribosome at the A site. To add an amino acid to a growing peptide chain, a charged tRNA enters the A site by base-pairing with the complementary codon on the mRNA molecule. Its amino acid is then linked to the growing peptide chain, which is held in place by the tRNA in the neighboring P site. Next, the large ribosomal subunit shifts forward, moving the spent tRNA to the E site before ejecting it. This cycle of reactions is repeated each time an amino acid is added to the polypeptide chain.
Which of these statements about facilitated diffusion across a membrane is true?
A specific membrane protein lowers the activation energy for movement of the solute through the membrane.
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
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.
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
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.
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 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.
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.
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).
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.
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.
Which of the following results in increased disorder? A. dissolving salt in water B. joining two sugars to make a sucrose molecule C. carrying out protein synthesis D. compressing a spring to a tense state
A. dissolving salt in water
A sodium-potassium antiport maintains the extracellular concentration of sodium at levels that are about 20-30 times higher than inside the cells. What directly supplies the energy for maintaining this gradient?
ATP hydrolysis drives the function of the pump.
What are all cell membranes composed of?
All cell membranes are composed of lipids and proteins and share a common general structure.
Which statement represents the cell theory?
All cells are formed by the growth and division of existing cells.
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)
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
D
A eukaryotic gene is observed to make multiple forms of a protein. How can one eukaryotic gene produce multiple products in the same cell?
Alternative splicing sites can lead to the production of two different mature mRNAs from the same gene, resulting in slightly different proteins.
Four step cycle during elongation (Translation)
Aminoacyl-tRNA binds to vacant A site on the ribosome, Large subunit of the ribosome translocates, moving the bound tRNAs to the E and P sites, Small subunit of the ribsome translocates ejecting the tRNA into the E site
Lipid bilayer:
Amphipathic molecules, are subject to two conflicting forces: the hydrophilic head is attracted to water, while the hydrophobic tails shun water and seek to aggregate with other hydrophobic molecules(like the fats in animals cells and the oils in plant seeds). This conflict is resolved by the formation of a lipid bilayer-and arrangement that is energetically favorable. With the hydrophilic heads facing water on both surfaces of the bilayer; and the hydrophobic tails being shielded from the water, as they lie next to one another in the interior.
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
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?
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.
The Translation II animation shows the arginine aminoacyl-tRNA entering the A site and arginine being added to the growing polypeptide. What would be the consequence of an alteration in the arginine tRNA anticodon sequence from UCC to ACC? Note the following mRNA codons: Arginine: AGA, AGG, CGU, CGC, CGA, CGG Threonine: ACU, ACC, ACA, ACG Tryptophan: UGG
Arginine will occasionally be added to the growing peptide in place of tryptophan. Changing the tRNA anticodon does not alter the amino acid that is added to that tRNA, so the mutated tRNA in this question will still be bound to arginine. The altered anticodon will no longer bind to the AGG codon for arginine in the mRNA. Instead, this altered tRNA will bind to the UGG codon in mRNA and add an arginine instead of the normal tryptophan. This will occasionally lead to arginine being added in place of tryptophan in the growing polypeptide. The actual tryptophan-charged tRNA is still in the cell, so sometimes the correct tryptophan will also be added to the growing polypeptide.
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.
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.
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+
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
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)
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.
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.
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.
C
Noncoding RNAs include all of the following EXCEPT A. rRNA. B. tRNA. C. mRNA. D. regulatory RNAs.
C
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
C
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.
C
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.
C
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.
C
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.
C
The nucleotide sequence of the template strand of DNA in a DNA double helix is 5ʹ-CAGAGGAATTTTCTG-3ʹ. What is the sequence of the resulting RNA molecule?
CAGAAAAUUCCUCUG
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.
Different molecules diffuse through the cytosol at different speeds. Which series represents the correct order in which molecules will diffuse from the fastest to the slowest?
CO2, tyrosine, succinate dehydrogenase, ribosome
Which of the following ions has a low cytosolic concentration so that a flood of this ion into the cell can be used as a signal for cell processes like fertilization?
Ca2+
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.
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?
Certain proteins easily aggregate with other proteins
(Q003) 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?
Certain proteins easily aggregate with other proteins.
A) false B) false D) false
Consider two genes that are next to each other on a chromosome, as arranged in the figure below True or False? a. The two genes must be transcribed into RNA using the same strand of DNA. b. If gene Thor is transcribed in a cell, gene Wasp cannot be transcribed. d. If gene Thor is transcribed in a cell, gene Wasp must be transcribed.
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).
What determines the nucleotide sequence of a newly transcribed RNA molecule?
Complementary base-pairing with a DNA during transcription Complementary base-pairing with DNA during transcription is what determines the nucleotide sequence of a newly transcribed RNA molecule. RNA polymerase uses the information—that is, the nucleotide sequence of the template strand of DNA—to synthesize a complementary RNA molecule.
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
D
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.
D
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.
D
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′
D
Protein concentration can be regulated by all of the steps listed EXCEPT A. nuclear export. B. RNA processing. C. mRNA stability. D. DNA replication.
D
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
D
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
D
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
In the presence of high levels of ___________, the enzyme phosphofructokinase is inhibited. A) glucose B) ADP C) fructose D) ATP
D) ATP
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.
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
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.
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
(Q013) 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.
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.)
What kind of membrane do eukaryotes have?
Eukaryotic cells have the plasma membrane as well as internal membranes that enclose intracellular compartments. The internal membranes form various organelles, including endoplasmic reticulum, Golgi apparatus, peroxisome, lysosome, transport vesicle, and two of these organelles are enclosed by two membranes, the mitochondria and nucleus.
Activation of the Polycomb complex is associated with euchromatin formation and gene silencing.
False
Eukaryotic promoters always require all four core promoter elements (-35, -30, start site, and +30) in order for RNA polymerase to initiate transcription.
False
Action potentials are usually mediated by voltage-gated Ca2+ channels.
False - voltage-gated Na+ channels
Determine whether the following statement is true or false: During translation, the growing peptide chain is always held together by the tRNA in the P site of the ribosome.
False- During translation, the growing peptide chain is not always held together by the tRNA in the P site of the ribosome. Rather, the growing peptide chain is held by either the tRNA in the P site or the tRNA in the A site.
Determine whether the following statement is true or false: Because introns are largely genetic junk, they do not need to be removed with any degree of precision during RNA splicing.
False- Introns must be removed precisely; removing even one nucleotide too many—or leaving an intronic nucleotide in the spliced mRNA—would shift the reading frame. Leaving larger pieces of intron in the mature mRNA would code for the insertion of extra amino acids. In either case, the consequences of imprecise splicing would be the production of an aberrant protein.
(Q015) The organelle shown in the figure is the ___________ and one of its main functions is to ___________.
Golgi apparatus; package and modify proteins for secretion
(Q013) For the following uncatalyzed reaction at equilibrium, how would the reaction change if it was now an enzyme-catalyzed reaction at equilibrium?
Forward reaction A would increase.
List three ways in which the process of eukaryotic transcription differs from the process of bacterial transcription.
Happens in nucleus of eukaryotes and cytoplasm in prokaryotesRNA processing events in eukaryotes and No RNA processing events in prokaryotesRNA polymerase - only 1 in prokaryotes - 3 in eukaryotesRNA polymerase can't start transcription on its own in eukaryotes need general transcription factorsMechanism that controls transcription is very elaborate in EukaryotesEukaryotes have to deal with chromatin structure
Hypoacetylated histone tails are usually associated with
Heterochromatin. Genes with low levels of expression.
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.
Membrane Assembly Begins in the ER:
In eukaryotic cells, new phospholipids are manufactured by enzymes bound to the cytosolic surface of the endoplasmic reticulum. Using free fatty acids as substrates, the enzymes deposit the newly make phospholipids exclusively in the cytosolic half of the bilayer, but cell membranes still grow evenly. The transfer of mono lipids from one monolayer to the other is usually done by being catalyzed by enzymes called scramblases, which remove randomly selected phospholipids from one half of the lipid bilayer and insert them in the other. This scrambling causes the newly made phospholipids to be redistributed equally between each monolayer of the ER membrane. Some of this newly assembled membrane will remain in the ER; the rest will be used to supply fresh membrane to other compartments in the cell. Bits of membrane are continually pinching off the ER to form small spherical vesicles that then fuse with other membranes, such as those of the Golgi apparatus.
Which of these is a general feature of the lipid bilayer in all biological membranes?
Individual lipid molecules are free to diffuse laterally in the surface of the bilayer.
enes in eukaryotic cells often have intronic sequences coded for within the DNA. These sequences are ultimately not translated into proteins. Why?
Intronic sequences are removed from RNA molecules by the spliceosome, which works in the nucleus.
Part of gene in eukaryotes that are transcribed into RNA
Introns and exons
In eukaryotes, which parts of a gene are transcribed into RNA?
Introns and exons- In eukaryotes, the introns and the exons of a gene are transcribed into RNA. This initial product is spliced into mature mRNA before the molecule is exported from the nucleus. Introns are spliced out by the activity of the spliceosome, leaving only exons in the mature mRNA.
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.
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. This antibiotic likely blocks translocation of the large ribosomal subunit (step 3 in the figure below), preventing the movement of peptidyl-tRNA from the A site to the P site of the ribosome. The two-amino-acid peptide can form because the initiator tRNA that carries methionine will bind to the P site, and the A site can accomodate the tRNA that recognizes UUU (which codes for phenylalanine). Because the ribosome can't translocate, no additional amino acids can be added. Translocation inhibitors are a known mechanism of action for antibiotics. An example of an antibiotic that uses this mode of action is cycloheximide.
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.
Which of the following is a function of the protein component of chromosomes?
It packages the DNA strands.
What does the plasma membrane do?
It serves as a barrier to prevent contents of the cell from escaping and mixing with the surrounding medium. It is penetrated by highly selective channels and transporters(proteins that allow specific, small molecules and ions to be imported and exported), which allow the exchange for nutrients to pass inward across the pasma membrane, and waste products to pass out, all of which enable the cell to grow. Other proteins in the membrane act as sensors, or receptors, that enable the cell to receive information about changes in its environment and respond to them in the correct way. The plasma membrane also grows and changes shape when the cell does, it does this by enlarging its area by adding new membrane without ever loosing its continuity, and it can deform without tearing. If a membrane is pierced, it neither collapses like a ballon nor remains torn; it reseals quickly.
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.
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. RNA polymerase binds to promoter sequences in a specific orientation. The RNA polymerase will then move away from the promoter using the promoter-dictated directionality and uses the 3' to 5' strand as a template to make a new RNA in the 5' to 3' direction.
Shown below 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.
Which ion is generally maintained at a high concentration inside the cell and a low concentration outside the cell?
K+
Which of the following is NOT used as a source of energy by a transmembrane pump to actively transport a solute?
K+
On the N-terminal tail of histone 3, which two lysines can either acetylated or methylated? (choose both correct answers, no partial credit)
K9 K27
Once researchers identified DNA as the unit of inheritance, they asked how information was transferred from the DNA in the nucleus to the site of protein synthesis in the cytoplasm. What is the mechanism of information transfer in eukaryotes?
Messenger RNA is transcribed from a single gene and transfers information from the DNA in the nucleus to the cytoplasm, where protein synthesis takes place.
(Q019) Which of the following is a role of the cytoskeleton in plant cells?
Microtubules form tracks for movement of cell components.
Amphipathic:
Molecules with both hydrophilic and hydrophobic parts are called amphipathic.
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.
How many different aminoacyl-tRNA synthetases do most organisms have?
One for each amino acid. Because there are 20 common amino acids found in proteins, there are 20 different aminoacyl-tRNA synthetase enzymes, as each one must recognize the appropriate amino acid along with the appropriate tRNA molecule.
At what site does the charged initiator tRNA first bind on the ribosome?
P site
Site charged initiator tRNA first bind on the ribosome
P site
At what site does the charged initiator tRNA first bind on the ribosome?
P site- In addition to a binding site for an mRNA molecule, each ribosome contains three binding sites for tRNA molecules, called the A site, the P site, and the E site. The charged initiator tRNA first binds on the ribosome at the P site. In eukaryotes, the initiator tRNA is charged with methionine and is loaded into the P site of the small ribosomal subunit, along with additional proteins called translation initiation factors. This small ribosomal subunit, with the initiator tRNA loaded into the P site, binds to the 5ʹ end of an mRNA molecule by recognizing the 5ʹ cap that is present on all eukaryotic mRNAs. To add an amino acid to a growing peptide chain, a charged tRNA enters the A site by base-pairing with the complementary codon on the mRNA molecule. Its amino acid is then linked to the growing peptide chain, which is held in place by the tRNA in the neighboring P site. Next, the large ribosomal subunit shifts forward, moving the spent tRNA to the E site before ejecting it. This cycle of reactions is repeated each time an amino acid is added to the polypeptide chain.
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.
Which biochemical reaction is catalyzed by a ribozyme?
Peptide bond formation in protein synthesis- Peptide bond formation in protein synthesis is catalyzed by a ribozyme. When the tRNA molecules associate with the mRNA, the rRNA of the ribosomal subunits orients the newly incoming amino acid with the growing peptide chain in a way that encourages the addition reaction between the two. Even though the ribosome is composed of both RNA and protein, the peptidyl transferase reaction is accomplished by the RNA, not protein, component of the ribosome.
(Q020) A nucleotide is different from a nucleoside because a nucleotide has a
Phosphate group(s)
What is the most common phospholipid in cell membranes?
Phosphatidylcholine, and it is build from five parts: they hydrophilic head, which consists of a choline linked to a phosphate group; two hydrocarbon chains, which form the hydrophobic tails; and a molecule of glycerol, which links the head to the tails. Each of the hydrophobic tails is a fatty acid-a hydrocarbon chain with a -COOH group at one end-which has been attached to glycerol via this group. A kink in one of the hydrocarbon chains occurs where there is a double bond between two carbon atoms. The "phosphatidyl" part of the name of a phospholipid refers to the phosphate-glycerol-fatty acid portion of the molecule.
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
Membrane lipids that are amphipathic:
Phospholipids, cholesterol(which is found in animal cell membranes), glycolipids(which have sugarer as part of they hydrophilic head).
(Q022) Genome size does not precisely determine gene number, as illustrated in the table below. What is a plausible explanation as to why A. thaliana, a plant, has a similarly sized genome as the fruit fly, but twice the number of protein-coding genes?
Plants have more genes that were duplicated during evolution.
Which bond term describes a covalent bond in which electrons are shared unequally?
Polar
Which of the following is true about "junk DNA"?
Portions of junk sequence are conserved between species and thus may be functional.
Which regulatory element does the RNA polymerase bind to?
Promoter
What is the name of the complex that degrades proteins that have reached the end of their lifespan, are damaged or are misplaced?
Proteasomes
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.
(Q021) What is one of the main differences between DNA and RNA?
RNA has two hydroxyl groups on the sugar, DNA has one.
What is one of the main differences between DNA and RNA?
RNA has two hydroxyl groups on the sugar, DNA has one.
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.
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.
Introns are removed by which of the following?
RNA splicing in the nucleus- Introns are removed by RNA splicing in the nucleus. In fact, the factors responsible for splicing sit on the tail of RNA polymerase II, the enzyme responsible for carrying out transcription of protein-coding genes. Therefore, as soon as the transcript begins elongating, it quickly receives a 5' cap and then begins splicing to remove introns, even while transcription continues. After splicing, the 3' end of the transcript is also modified and then the mature mRNA is exported to the cytosol for translation.
Characteristic of a replicating RNA polymerase that allows multiple transcripts to be made simultaneously from the same region of DNA
RNA transcript dissociates from DNA template immediately once complete
Which of the following statements is supported by the information in this image and is consistent with your knowledge regarding genomic architecture in prokaryotes and eukaryotes?
The eukaryotic cell must have a nuclear spliceosome to remove introns from RNA.
Which macromolecule(s) is/are critical in the active site of the ribosome for catalysis of peptide bond formation?
Ribosomal RNA- The ribosomal RNA is the critical component in the active site as this site is made of only ribosomal RNA. The protein helps support the RNA but does not participate in the catalysis of peptide bond formation. The ribosomal RNA base-pairs with the tRNA holding the growing polypeptide, helping to position it in the correct orientation. Other RNA nucleotides base-pair with the incoming tRNA to position the amino acids. Further hydrogen-bonding positions the amino acids, facilitating new peptide bond formation.
An RNA message is decoded by which of the following?
Ribosomes. Protein synthesis, which is also called translation, is the "decoding" process that is carried out by the peptidyl transferase activity of the ribosome. Ribosomes bind to mRNA and allow for a charged tRNA with the complementary anticodon to recognize a particular mRNA codon and then transfer the amino acid to the growing polypeptide chain.
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).
It would use the bottom strand because the promoter sets the direction and the polymerase moves from 3′ to 5′ along the template strand.
Shown below 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?
site 3 ( letter C in 3' - 5')
Shown below is a tRNA for tryptophan. Which of the locations on the tRNA accommodates looser base-pairing rules?
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.
Which one of the following statements about membranes is true?
Sterol lipids are common in human cell plasma membranes.
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
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
What can happen if heterochromatin spreads inappropriately into an area with active genes?
The active genes can become silenced.
Some antibiotics function by inhibiting translation. One class blocks the interaction between EF-Tu and the aminoacyl-tRNA. What specific effect would this have on the ribosome and translation?
The aminoacyl-tRNA will not enter the A site on the ribosome. EF-Tu binds to free aminoacyl-tRNAs and helps deliver them to the A site of the ribosome. If the anticodon is compatible with the codon of the mRNA, the tRNA binds in the A site and EF-Tu hydrolyzes GTP to dissociate. Free aminoacyl-tRNAs do not enter the A site alone. One class of antibiotics binds to EF-Tu and blocks the binding to aminoacyl-tRNAs. This has the effect of blocking translation since aminoacyl-tRNAs do not enter the A site on their own, thus halting translation.
(Q012) 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. ΔG = ΔG° + RT ln
The amount of product will be higher than the amount of substrate at equilibrium.
What does the fluidity of a lipid bilayer depend on?
The fluidity of a lipid bilayer depends on its phospholipid composition, and the nature of the hydrocarbon tails: the loser and more regular the packing of the tails. the more viscous and less fluid the bilayer will be. Two major properties of hydrocarbon tails affect how tightly they pack in the bilayer: their length and the number of double bonds they contain. A shorter chain length reduces the tendency of the hydrocarbon tails to interact with one another and therefore increases the fluidity of the bilayer. The hydrocarbon tails of membrane phospholipids vary in length between 14 and 24 carbon atoms, with 18-20 atoms being the most usual. Most phospholipids contain one hydrocarbon tails that has one or more double bonds between adjacent C atoms, and a second tail with single bonds. The chain that harbors a double bond does not contain the maximum number of H atoms that could be attached to its C backbone; and thus is said to be unsaturated with respect to H. The hydrocarbon tail with no double bonds has a full complement of H atoms and is said to be saturated. Each double bond in an unsaturated tail creates a small kink in the tail, which makes it more difficult for the tails to pack against one another, and therefore the lipid b players that contain a large proportion of unsaturated hydrocarbon tails are more fluid that those with lower proportions. In bacterial and yeast cells, which have to adapt to varying temperatures, both the lengths and the unsaturation of the hydrocarbon tails in the bilayer are constantly adjusted to maintain the membrane at a relatively constant fluidity: at higher temperatures, the cell makes membrane lipids with tails that are longer and that contain fewer double bonds.
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.)
(Q019) 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 to ADP caused a conformational change in the protein.
To which part of an mRNA molecule do ribosomal subunits first bind?
The initial binding site for a ribosome is the 5' end of an mRNA molecule, upstream of the important AUG that serves as the start translation signal. Initiation of translation is outlined in the steps shown in the figure below. Pay special attention to how the small ribosomal subunit, pre-loaded with an initiator tRNA and other translation initiation factors, binds to the 5' untranslated region and then slides along the mRNA until it reaches the start AUG codon. Once this happens, the rest of the ribosome complex can assemble so that translation can begin in earnest.
Which of these statements about the composition of membranes is true?
The inner and outer membranes of mitochondria have different protein compositions.
Structure of lipids in a cell membrane:
The lipids in a cell membrane are arranged in two closely apposed sheets, forming a lipid bilayer. Which serves as a permeability barrier to most water-soluble molecules. Each single lipid molecule has a hydrophilic (water-loving) head and a hydrophobic (water-fearing) tail.
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 would be more deleterious than the loss of three nucleotides in that same region because removing a single nucleotide from the protein-coding region of a gene would alter the reading frame in the mRNA. Such mutations cause every codon in the mRNA to be misread and produce a protein with a garbled and nonfunctional sequence of amino acids. In some cases, the resulting protein is even shortened, as the change in reading frame can introduce premature stop codons. Removing three nucleotides—or one codon—from the mRNA produces a protein that is missing a single amino acid. Unless that amino acid is critical for the activity or folding of the protein, the mutation will have little effect on protein function.
In an experimental situation, a student researcher inserts an mRNA molecule into a eukaryotic cell after she has removed its 5' cap and poly-A tail. Which of the following would you expect her to find?
The molecule is digested by enzymes because it is not protected at the end.
What are the most abundant lipids in cell membranes?
The most abundant lipids in cell membranes are the phospholipids, which has a phosphate-containing, hydrophilic head linked to a pair of hydrophobic tail. EX-phosphatidylcholine has the small molecule choline attached to a phosphate group as its hydrophilic head.
(Q018) Why is the oxidation of NADPH energetically favorable?
The oxidized form of NADPH is more stable than the reduced form.
In an experiment conducted in 1962, investigators took tRNAs bearing cysteine and chemically converted the charged amino acid to an alanine. They then introduced these "hybrid" alanine-bearing tRNAs into a cell-free translation system from which they removed all of the normal, cysteine-bearing tRNAs. How did this chemical manipulation affect the proteins produced by this altered system?
The proteins contained alanines where cysteines were supposed to be. This experiment demonstrated that ribosomes do not "check" the identity of the amino acids attached to tRNAs. Unlike DNA polymerase, ribosomes do not have a proofreading mechanism that ensures proper sequence of the product. Once an amino acid has been coupled to a tRNA, the ribosome will "blindly" incorporate that amino acid into the position dictated by the codon-anticodon match. It also reinforces the crucial role that the aminoacyl-tRNA synthetases play in the accuracy of translation. Thus, the tRNA is involved in two equally important recognition events: (1) the proper charging of the tRNA by an aminoacyl-tRNA synthetase, and (2) the proper anticodon recognition when a message is within the ribosome.
(Q015) Which of the following is a reason why ATP hydrolysis has a negative ΔG0?
The removal of the phosphate is energetically favorable.
Lipid bilayers are self-sealing:
The same forces that drive the amphipathic molecules to form a bilayer help to make the bilayer self-sealing. Any tear in the sheet will create a free edge that is exposed to water, and this situation is energetically unfavorable, so the molecules of the bilayer will spontaneously rearrange to eliminate the free edge. If the tear is small, this spontaneous rearrangement will exclude the water molecules and lead to repair of the bilayer, restoring a single continuous sheet. If the tear is large, the sheet may begin to fold in on itself and break into separate closed vesicles, either way, the free edges are quickly eliminated. The only way a finite amphipathic sheet can avoid having free edges is to bend and seal, forming a boundary around a closed space, so phospholipids necessarily assemble into self-sealing containers that define close compartments.
What kind of membrane does the simplest bacteria have?
The simplest bacteria have only a single membrane, the plasma membrane.
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.
To crack the genetic code, researchers introduced synthetic messenger RNAs into in vitro translation systems and determined which proteins were produced from these synthetic mRNAs. mRNAs consisting of poly-UUC led to production of three different proteins: poly-Phe, poly-Ser, and poly-Leu. What best explains this result?
The synthetic mRNA was read in all three reading frames. The genetic code does not change in vitro as compared to in vivo. However, unlike when in vivo, in which translation begins at an initiating methionine start codon, when in vitro, the ribosome can be forced to translate any message in all three reading frames. Thus the UUCUUCUUCUUC message was read three different ways. Starting at the first U, UUC codes for Phe, as shown in the figure. If the ribosome started at the second U, the message was read as repeating UCU codons, so poly-Ser was produced. In the third reading frame, the ribosome read the message as repeating CUU codons, resulting in poly-Leu.
Most cell membranes are asymmetrical:
The two halves of the bilayer often include very different sets of phospholipids. This asymmetry begins in the Golgi apparatus, this membrane contains another family of phospholipid-handling enzyme, called flippases. These enzymes remove specific phospholipids from the side of the bilayer facing the exterior space and flip them into the monolayer that faces the cytosol. The action of these flippases and similar enzymes in the plasma membrane initiates and maintains the asymmetric arrangement of phospholipids of the membranes in animal cells. This asymmetry is preserved as membranes bud from one organelle and fuse with another-or with the plasma membrane. This means that all cell membranes have distinct "inside" and "outside" faces: the cytosolic monolayer always faces the cytosol, while the noncytosolic monolayer is exposed to either the cell exterior-in the case of the plasma membrane- or to the interior space(lumen) of an organelle. This conversion applies not only to the phospholipids that make up the membrane, but to any proteins that might be inserted in the membrane, the positioning of proteins is crucial for their function.
Referring to the DNA double helix, what does the term "anti-parallel" mean?
The two strands are arranged in opposing 5' to 3' orientations.
According to the current model for HIV infection, which of the following is not involved in the process of membrane fusion?
The viral chromosome
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.
Why do phospholipids aggregate to form cell membranes?
They are amphipathic.
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.
What is true of eukaryotic mRNAs?
They are translated after they are exported from the nucleus. Unlike prokaryotes, where transcription and translation can occur simultaneously, these two events are separated in time and space in eukaryotes. In eukaryotes, transcription takes place in the nucleus and the transcript must also undergo processing here to become a mature mRNA. After this occurs, the mRNAs are exported to the cytosol where they interact with ribosomes to carry out translation.
(Q014) What is the role of activated carriers in cells?
They capture energy from energy releasing reactions and transfer it to other reactions.
What is the role of activated carriers in cells?
They capture energy from energy releasing reactions and transfer it to other reactions.
Which of the following is true about amyloid protein structures?
They consist of stacked β sheets
(Q005) Which of the following is true about amyloid protein structures?
They consist of stacked β sheets.
How many nucleotides are necessary to specify a single amino acid?
Three- Three nucleotides are necessary to specify a single amino acid, and these groupings of three nucleotides are referred to as codons. With four different bases to choose from (A, U, C, G), the combination of three nucleotides is the smallest grouping to provide enough diversity to code for all 20 different amino acids: 4 × 4 × 4 = 64 different possible codon sequences. 64 codons is larger than the number of different amino acids (20), which means that many of the amino acids have more than one codon that will specify their placement into a polypeptide.
In principle, how many reading frames in an RNA molecule can potentially be translated into protein?
Three- Translation functions in a manner analogous to reading an mRNA sentence that is made up of several three-letter words (codons). If translation starts on the second or third letter of the first word and then starts "reading" words in three-letter groupings, a completely different "sentence" (protein) results. If translation begins on the fourth nucleotide in this mRNA "sentence," the words that it "reads" are back to placing the same amino acids as the first line, because the genetic code works based off of triplet codons. These three potential starting points, each potentially resulting in its own unique amino acid sequence, are what is called reading frames. In reality, only one of the three reading frames will result in the translation of the proper protein.
Export of RNA from the nucleus requires the RNA to have which characteristic(s)?
To be exported, RNAs must have the features of a processed mRNA. This includes being properly spliced (no introns), having a 5' cap and a poly-A tail.
The process of gene expression always involves which process(es) described in the central dogma?
Transcription
The process of gene expression always involves which process(es) described in the dogma?
Transcription
At which step of gene expression can cells amplify the number of copies of a protein made from a single gene?
Transcription and translation- Proteins can be made in large quantities by transcribing many mRNAs from the gene, and then each mRNA can be translated into many copies of the protein. In contrast, if just a few mRNAs are made, only a few copies of the protein are made.
A DNA sequence might be the promoter that drives expression of a dynein motor gene. You make a mutation that removes the sequence TATATAT from the −25 region of this putative promoter. If the original sequence serves as a promoter, what should happen to transcription of the dynein motor gene in the mutant?
Transcription should decrease.
(Q016) Which way do the fatty acid tails of a phospholipid face in a cell membrane?
both directions
In RNA, which nitrogenous base will pair with the base A?
U
Leu, Ser
Using the genetic code below, determine the amino acids that a polynucleotide of UC would code for.
Investigators treat cells with a chemical that introduces random mutations into the DNA, including single-nucleotide changes that turn one base into another. They then isolate two mutants: one produces a protein that carries an alanine at a site that normally contains a valine; the other produces a protein that carries a methionine instead of the valine. When these mutant cells are subjected to the same mutagenic treatment, they both produce proteins that contain a threonine at the site of the original valine. Assuming that the mutations causing these alterations are single-nucleotide changes, what were the codons that specified each of the amino acids discussed?
Val, GUG; Ala, GCG; Met, AUG; Thr, ACG Methionine is specified by a single codon, AUG, because it also always functions as the start translation codon. This provides a starting point to solve the rest of the question. Working backward from the methionine AUG, the codon specifying valine must have been GUG (the mutation having changed the initial G to an A). If that is the case, the codon specifying alanine must be GCG (the mutation having changed the U in GUG to a C in GCG). Finally, the codon specifying threonine must be ACG (one mutation changing AUG to ACG, the other changing GCG to ACG). Each of these was one nucleotide positon off from the other.
How is an electrical signal converted to a chemical signal at a nerve terminal?
Voltage-gated Ca2+ channels are activated and the influx of Ca2+ triggers the release of neurotransmitters.
How are voltage-gated ion channels opened by voltage sensors?
When membrane potential changes sufficiently, the electrical force causes voltage sensor domains to change conformation.
What is the "central dogma"?
Within the cell, genetic information flows from DNA to RNA to protein.
Which organism would be the most useful for studying how mutations that cause sudden death in young athletes can affect the development of the heart?
Zebrafish While zebrafish and humans might seem quite different from one another, compared to the other model organisms listed in this question, the zebrafish is the most closely related to humans as both species are vertebrates. Additionally, the zebrafish has distinct advantages for studying aspects of development, including their quick gestation time and the fact that they are transparent for the first two weeks of life, making observation of cells and tissues easier. This makes zebrafish the most useful organism among the choices listed for studying how mutations that cause sudden death in young athletes can affect the development of the heart.
An integral membrane protein can be extracted with:
a solution containing detergent.
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 FEEDBACK: ATP powers the formation of energetically unfavorable bonds between two molecules by first breaking its own high-energy phosphoanhydride bond and transferring the phosphate to another molecule. This new phosphate linkage can then be broken to power the bond formation between molecules.
A ligand-gated ion channel (such as the nicotinic acetylcholine receptor) is:
a membrane protein that permits an ion to pass through the membrane only when opened by the appropriate ligand.
(Q007) Which of the following is UNLIKELY to be hydrophilic?
a molecule with primarily nonpolar covalent bonds
Which of the following is UNLIKELY to be hydrophilic?
a molecule with primarily nonpolar covalent bonds
The genetic code was originally deciphered, in part, by experiments in which synthetic polynucleotides with repeating sequences were used as mRNAs to direct protein synthesis in cell-free extracts. Under these conditions, ribosomes could be made to start translation anywhere within the RNA molecules, with no start codon necessary. What peptide would be made by translation from a synthetic mRNA made of the repeating dinucleotide CGCG...?
a peptide containing alternating arginines and alanines The sequence of nucleotides in an mRNA molecule is read consecutively in groups of three, termed codons. In this question, and depending on where translation begins along the repetitive polynucleotide CGCG..., two different codons are possible: CGC and GCG. These two codons specify arginine and alanine, respectively. The peptide produced would therefore contain alternating residues of these two amino acids. An mRNA sequence can be translated in any one of three different reading frames, depending on where the decoding process begins. However, in the cell, and unlike the synthetic example of this question, only one of the three possible reading frames in mRNA specifies the correct protein. A special signal at the beginning of each mRNA molecule sets the correct reading frame—the AUG start translation codon.
Which of the following would be able to cross a protein-free lipid bilayer most rapidly?
a steroid hormone (nonpolar, large)
The genetic code was originally deciphered, in part, by experiments in which synthetic polynucleotides with repeating sequences were used as mRNAs to direct protein synthesis in cell-free extracts. Under these conditions, ribosomes could be made to start translation anywhere within the RNA molecules, with no start codon necessary. What peptide would be made by translation from a synthetic mRNA made entirely of adenine (poly-A)?
a polymer of lysine: Lys-Lys-Lys... The genetic code was originally deciphered, in part, by experiments in which synthetic polynucleotides with repeating sequences were used as mRNAs to direct protein synthesis in cell-free extracts. Under these conditions, ribosomes could be made to start translation anywhere within the RNA molecules, meaning that no start codon was necessary. A polymer of lysine (Lys-Lys-Lys...) would be made by translation from a synthetic mRNA made entirely of adenine (poly-A). Because no start codon was necessary, the ribosome could recognize any of the three reading frames of this synthetic polynucleotide (...AAAAAAAAAAAAAAA...) and begin translation. Because the synthetic polynucleotide is just repeating adenines, all reading frames are "AAA," which codes for lysine. Similarly, a synthetic poly-U mRNA as shown below would yield a polymer composed entirely of phenylalanine.
The genetic code was originally deciphered, in part, by experiments in which synthetic polynucleotides with repeating sequences were used as mRNAs to direct protein synthesis in cell-free extracts. Under these conditions, ribosomes could be made to start translation anywhere within the RNA molecules, with no start codon necessary. What peptide would be made by translation from a synthetic mRNA made of the repeating trinucleotide UCGUCG...?
a polymer of serine (Ser-Ser-Ser...), a polymer of arginine (Arg-Arg-Arg...), and a polymer of valine (Val-Val-Val...) Write out the sequence UCGUCGUCGUCGUCGUCG. This represents six iterations of the same repeated triplet. Now, identify the three different reading frames and determine if they are similar or different. In principle, an mRNA sequence can be translated in any one of three different reading frames, depending on where the decoding process begins. For the peptides produced by translation from a synthetic mRNA made of the repeating trinucleotide UCGUCG..., a polymer of serine (Ser-Ser-Ser...), a polymer of arginine (Arg-Arg-Arg...), and a polymer of valine (Val-Val-Val...) are expected. This is because each of the three reading frames will be read but each will generate a distinct polypeptide. In one reading frame, the sequence UCGUCGUCG... codes for a polymer of serine; in another, the sequence CGUCGUCGU... codes for a polymer of arginine; and in the final one, the sequence GUCGUCGUC... codes for a polymer of valine. Thus, a mixture of the three different peptides will be produced.
Consider the transport of glucose into an erythrocyte by facilitated diffusion. When the glucose concentrations are 5 mM on the outside and 0.1 mM on the inside, the free-energy change for glucose uptake into the cell is: (These values may be of use to you: R = 8.315 J/mol·K; T = 298 K; 9 (Faraday constant) = 96,480 J/V; N = 6.022 1023/mol.)
about 10 kJ/mol.
Consider the transport of K+ from the blood (where its concentration is about 4 mM) into an erythrocyte that contains 150 mM K+. The transmembrane potential is about 60 mV, inside negative relative to outside. The free-energy change for this transport process is: (These values may be of use to you: R = 8.315 J/mol.K; T = 298 K; 9 (Faraday constant) = 96,480 J/V; N = 6.022 1023/mol.)
about 15 kJ/mol.
(Q008) A base is a molecule that will ___________ a proton in water.
accept
A base is a molecule that will __________ a proton in water.
accept
(Q019) Amino acids with side chains that contain −COOH groups, like those shown below, would be ___________ in the aqueous environment of a cell.
acidic
Amino acids with side chains that contain −COOH groups, like those shown below, would be ___________ in the aqueous environment of a cell.
acidic
Some, such as ____________ help with muscle contraction and cell movement.
actin
You have developed a promising anti-cancer agent, but it has poor solubility in water. Which of the following changes should improve water solubility?
adding a carboxyl group adding a hydroxyl group
Amino acids are attached to their tRNA molecules by which of the following?
aminoacyl-tRNA synthetases- For translation to accurately transmit the protein-coding information contained within a gene, there needs to be a direct, linear relationship between the mRNA codon, a tRNA anticodon, and the amino acid attached to the tRNA. The recognition of a codon by the anticodon is accomplished through complementary base-pairing. However, the attachment of the proper amino acid to a tRNA harboring the correct anticodon specificity is accomplished by a group of enzymes known as aminoacyl-tRNA synthetases. Cells have enough different versions of this enzyme so that there is a separate enzyme for recognizing each anticodon and then covalently attaching the appropriate amino acid. Once the amino acid has been linked to the tRNA, the tRNA is said to be "charged" and is ready to bind its specific codon on the ribosome-bound mRNA, resulting in the addition of the proper amino acid to the growing polypeptide chain.
Detergent molecules are ___________ in nature and bind with membrane proteins and membrane lipids to disrupt their interactions and release the proteins from the membrane.
amphipathic
Within the ribosome, the formation of peptide bonds is catalyzed by what component?
an RNA molecule in the large ribosomal subunit- The eukaryotic ribosome is a large complex of four rRNAs and more than 80 small proteins, arranged into two subunits: the large and the small ribosomal subunits. The small ribosomal subunit matches the tRNAs to the codons of the mRNA, while the large subunit catalyzes the formation of the peptide bonds that covalently link the amino acids together into a polypeptide chain. The peptidyl transferase activity of the ribosome is responsible for formation of the peptide bonds in the growing polypeptide.
The fluidity of the lipid side chains in the interior of a bilayer is generally increased by:
an increase in the number of double bonds in fatty acids.
Which of the following does not increase the stability of eukaryotic mRNAs?
an intron
(Q001) Reactions that build larger molecules in the cell are called ___________; reactions that break down molecules into smaller ones are called ___________.
anabolic; catabolic
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- RNA capping, a part of RNA processing, takes place as an RNA is being transcribed. Eukaryotic genes contain both introns and exons, and both are transcribed. Soon after transcription begins, within the first 25 nucleotides added to the growing RNA strand, a modified guanine nucleotide is added to the 5' end of the RNA. Once the cap is added and as transcription is continuing along the gene, splicing to remove introns can begin. After transcription is complete, further modification of the RNA transcript must occur, including the addition of the 3' poly-A tail, before the mature mRNA can exit the nucleus to be translated by ribosomes in the cytosol.
TATA box is not found in
bacteria
Heterochromatin can spread along a chromosome until it encounters a
barrier DNA sequence
The consistent diameter of the DNA double helix arises between of which property?
base pairing of pyrimidines with purines
A molecule with a lot of polar covalent bonds is likely to
be highly soluble in water
(Q006) A molecule with a lot of polar covalent bonds is likely to
be highly soluble in water.
If the backbone of a polypeptide is hydrophilic, how can a transmembrane alpha helix span the hydrophobic portion of the lipid bilayer?
because amino acid side chains in a transmembrane helix are hydrophobic and interact with the hydrophobic interior of the bilayer
Which way do the fatty acid tails of a phospholipid face in a cell membrane?
both directions
Polymers composed of monosaccharides are formed through ____________ reactions and are called ____________ . Specific forms of these polymers serve several different functions.
dehydration, polysacchrides
(Q006) Why is CO2 an end product of cellular respiration?
because it is the most stable form of carbon in our atmosphere
Why is CO2 an end product of cellular respiration?
because it is the most stable form of carbon in our atmosphere FEEDBACK: Cellular respiration is the breakdown of carbon-containing molecules through oxidation to release energy. Because the most energetically stable form of carbon in the presence of oxygen is carbon dioxide, this is the final end product of respiration.
(Q003) 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 sunlight the ultimate source of energy for nearly all living things on Earth?
because photosynthetic organisms produce food molecules using light energy FEEDBACK: Organic molecules for energy are obtained by animals through their diet, by consuming either plants or animals that eat plants. Plants produce organic molecules using energy from the sun, thus the source of energy from food molecules in plants is ultimately from the sun.
Which of the following is a common transmembrane protein structure that can traverse the membrane to form a pore or channel by alternating hydrophobic and hydrophilic amino acids? An example of this is a porin protein.
beta barrel
(Q001) The chemical reactions that take place in a cell, as compared to the chemistry in nonliving matter, primarily occur
between carbon-based molecules.
Tetracycline is an antibiotic that inhibits bacterial protein synthesis by
blocking the binding of aminoacyl-tRNA to the A site of the ribosome
In animals, ____________ provides vital long-term energy storage.
blubber
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.)
(Q022) Which method is most suitable for determining the three-dimensional structure of an extremely large integral membrane protein complex?
cryoelectron microscopy
These subunits attach themselves together to build biomolecules through ____________ reactions.
dehydration
A ____________ reaction joins the ____________ together, forming a(n) ____________ bond called a ____________ bond.
dehydration, amino acids, covalent, peptide
Facilitated diffusion through a biological membrane is:
driven by a difference of solute concentration.
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
The specificity of the potassium channel for K+ over Na+ is mainly the result of the:
differential interaction with the selectivity filter protein.
Combinations of two monomers are called ____________ and include molecules like ____________ , which are typically ____________ and can be metabolized into ____________ .
disaccharides, maltose, transported, fat
Reason why RNA polymerase makes more mistakes than DNA polymerase
does not have proofreading activity
A stretch of amino acids in a polypeptide chain that is capable of independently folding into a defined structure is called a
domain
(Q008) Which of the following shows protein organizational units in the correct order from smallest to largest?
domain < subunit < complex
(Q006) A stretch of amino acids in a polypeptide chain that is capable of independently folding into a defined structure is called a
domain.
What purpose does NADPH serve in biosynthetic reactions like the one pictured below?
donating electrons for a reduction reaction FEEDBACK: NADPH is a carrier of electrons that are used in reduction reactions often used in biosynthesis of molecules. In the process, NADPH donates electrons, and itself becomes oxidized to NADP+.
The structural feature of DNA that hints at the mechanism for its replication is the
double helix.
When they're exposed to water, they orient themselves in a ____________ layer, so that the ____________ face out towards the water or inside of the cell and the ____________ face each other.
double, heads, tails
What is the measure of disorder in a system called?
entropy
A process not involving the fusion of two membranes or two regions of the same membrane is:
entry of glucose into cells.
Many of these synthesis and degradation processes are catalyzed by ____________ .
enzymes
Proteins serve many diverse functions. Some function as ____________ , catalyzing metabolic reactions within cells.
enzymes
Glucose transport into erythrocytes is an example of:
facilitated diffusion.
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
The more double bonds within a ____________ tail, the ____________ the melting temperature.
fatty acid, lower
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
What performs the function of bacterial sigma factor in eukaryotes?
general transcription factors
What is responsible for moving glucose from the gut lumen into intestinal epithelial cells?
glucose-sodium symport
One ____________ molecule attaches to three ____________ molecules to form a ____________ .
glycerol, fatty acid, triglyceride
Animals use ____________ as a way to store glucose. It typically exists in a ____________ and is stored in the liver.
glycogen, branched form
Location of splicing of pre-mRNAs
in nucleus as RNA is still being transcribed
Where does the splicing of pre-mRNAs take place?
in the nucleus as the RNA is still being transcribed
Where does the splicing of pre-mRNAs take place?
in the nucleus as the RNA is still being transcribed- The splicing of pre-mRNAs takes place as the RNA is still being transcribed in the nucleus. RNA capping occurs early in transcription, after RNA polymerase has produced about 25 nucleotides of RNA. Splicing begins after capping takes place, and it removes the introns from the RNA transcript. After processing, which also includes the modification of the 3' end of the transcript with a poly-A tail, the now mature mRNA transcript can leave the nucleus and enter the cytosol for translation.
What is the conformation of the voltage-gated Na+ channel that keeps the action potential from traveling backward along the axonal membrane?
inactivated
If a reaction is energetically favorable (exergonic), then it must produce a(n)
increase in entropy FEEDBACK: Reactions that are energetically favorable increase the entropy (or disorder) of the universe. This can be through either the release of free energy in different forms, or the release of energy as heat (energy in its most disordered form).
(Q007) If a reaction is energetically favorable (exergonic), then it must produce a(n)
increase in entropy.
The fluidity of a lipid bilayer will be increased by:
increasing the temperature.
When a ligand binds to an allosteric enzyme's regulatory site, it changes the activity of that enzyme by
inducing a conformational change
(Q015) When a ligand binds to an allosteric enzyme's regulatory site, it changes the activity of that enzyme by
inducing a conformational change.
When a bacterium such as E. coli is shifted from a warmer growth temperature to a cooler growth temperature, it compensates by:
putting more unsaturated fatty acids into its membranes.
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.)
Integrins are:
membrane proteins that mediate cell adhesion.
In eukaryotes, the initiator tRNA always carries which amino acid?
methionine
In eukaryotes, the initiator tRNA carries what amino acid
methionine
Which of the following chemical groups could confer nonpolar/hydrophobic characteristics on the region of a molecule in which it is found?
methyl group (-CH3) Bonds between carbon and hydrogen are nonpolar and molecules with mostly nonpolar bonds are hydrophobic. Bonds between H and electronegative atoms like O and N are polar and tend to impart hydrophilic characteristics.
(Q012) Which of the following chemical groups could confer nonpolar/hydrophobic characteristics on the region of a molecule in which it is found?
methyl group (−CH3)
(Q018) Which of the following accurately matches the types of filaments in the cytoskeleton with their cellular function?
microtubules—chromosome segregation; intermediate filaments—strength/support; actin filaments—cell movement
The "threshold" potential of a membrane is the _____.
minimum depolarization needed to operate the voltage-gated sodium and potassium channels
Single monomers are called ____________ and include molecules like glucose, which are typically used for ____________ or to help build the backbone of nucleotides that make up RNA and DNA.
monosaccharides, immediate energy
(Q009) Compared to eukaryotes, prokaryotic organisms are
more abundant and more widespread on Earth.
A toxin that binds specifically to voltage-gated sodium channels in axons would be expected to _____.
prevent the depolarization phase of the action potential
(Q004) Cellular respiration ___________ energy and produces ___________, whereas photosynthesis ___________ energy and produces ___________.
produces; water + carbon dioxide; consumes; oxygen + sugars
Cellular respiration ___________ energy and produces ___________, whereas photosynthesis ___________ energy and produces ___________.
produces; water + carbon dioxide; consumes; oxygen + sugars FEEDBACK: Cellular respiration is the process by which cells break down food molecules for energy, producing water and carbon dioxide as waste products. Photosynthesis uses energy from the sun to make food molecules (sugars) and oxygen.
To begin transcription, eukaryotic RNA polymerase recognizes nucleotide sequences in what region of the DNA?
promoter region
To begin trasnscription, eukaryotic RNA polymerase recognizes nucleotide sequences in what region of DNA
promotor
Complex that degrades proteins that have reached the end of their lifespan, are damaged, or are misfolded
proteasome
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.
(Q003) Self-replication of living cells occurs through the catalytic action of
proteins.
(Q002) Two atoms held together solely by ionic bonds are referred to as a(n)
salt
Long noncoding RNA (lncRNA) can function as a(n)
scaffold for proteins.
(Q006) Which of the following microscopy techniques would allow the most detailed image showing the 3-D structure of a flagellum?
scanning electron microscopy
A phospholipid is inserted into the cytosolic side of the ER membrane. Which of the following could randomly reposition this phospholipid to the other (lumen) side of the ER membrane?
scramblase
Once amino acids begin to form bonds with one another to create helical or sheet-like formations, a ____________ structure is formed.
secondary
The type of membrane transport that uses ion gradients as the energy source is:
secondary active transport.
Ion channels contain a selectivity filter that
selects for positively charged ions by virtue of the negatively charged amino acids lining the pore, but allows similar ions through, like Na+ and K+.
(Q002) All living cells
share the same basic chemistry.
The "undershoot" phase of after-hyperpolarization is due to _____.
sustained opening of voltage-gated potassium channels
In mRNA codons in mRNAs bind to complementary anticodons in
tRNAs
Membrane fusion leading to neurotransmitter release requires the action of:
tSNARE and vSNARE
Which of the following is an inorganic compound?
table salt
(Q011) Which of the following is an inorganic compound?
table salt (e.g., NaCl)
which of the following is found only in eukaryotic genomes, and NOT in prokaryotic genomes?
telomeres
When amino acids bond further, creating a globular shape, this is referred to as a protein's ____________ structure.
teritary
At which site on the DNA of a gene does RNA polymerase release its newly made RNA
terminator
Site on the DNA of a gene that RNA polymerase releases newly made RNA
terminator
What is the molecular target of the antidepressant Prozac?
the symport that drives reuptake of serotonin
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. K=[x]/[y] ΔG = ΔG° + RT ln[x]/[y]
the amount of product will be higher than the amount of substrate at equilibrium FEEDBACK: If the equilibrium constant, K, is very high, it means that there is far more of the product X than substrate Y at equilibrium (i.e., when forward and reverse reaction rates are balanced). This corresponds to a free-energy change that is large and negative
In eukaryotes genes can be expressed simultaneously by
the binding of a specific transcriptional regulator to several genes
In eukaryotes, multiple genes can be expressed simultaneously by
the binding of a specific transcriptional regulator to several genes
In eukaryotes, multiple genes can be expressed simultaneously by
the binding of a specific transcriptional regulator to several genes.
(Q012) The Michaelis constant (KM) of an enzyme is a measure of
the binding strength of enzyme to substrate.
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.)
If a phospholipid is located in the outer layer of the bilayer in a vesicle, where will it end up when the vesicle fuses with the plasma membrane?
the cytosolic face of the bilayer
DNA is a better molecule for long term storage of genetic information that RNA because
the deoxyribose sugar stabilizes DNA chains.
DNA is a better molecule for long-term storage of genetic information than RNA because
the deoxyribose sugar stabilizes DNA chains.
All of the RNA in a cell is made by what process?
transcription
What is the source of energy that drives transcription elongation forward?
the hydrolysis of high-energy bonds of ribonucleoside triphosphates The source of energy that drives transcription elongation forward is the hydrolysis of high-energy phosphate bonds of ribonucleoside triphosphates that are being incorporated into the growing RNA molecule. The nucleoside triphosphate is hydrolyzed to yield a nucleoside monophosphate, which forms a phosphodiester bond with the free 3' hydroxyl end of the RNA polymer, and a pyrophosphate molecule, which is subsequently hydrolyzed into two molecules of inorganic phosphate. The breakdown of pyrophosphate into inorganic phosphate renders the polymerization reaction essentially irreversible. Because the energy to drive polymerization is delivered by the nucleoside triphosphates themselves, no additional energy is needed for the catalytic activity of RNA polymerase.
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.
Reading frame that is used for translating an mRNA into functional protein is determined by
the location of an AUG
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
Why is the oxidation of NADPH energetically favorable?
the oxidized form of NADPH is more stable than the reduced form. FEEDBACK: NADPH carries two high-energy electrons. Losing these electrons in an oxidation reaction is energetically favorable because the oxidized form, NADP+, is more stable than the reduced form (NADPH).
You have isolated a piece of DNA that you believe contains an interesting gene. Using a mix of RNA polymerase and ribonucleotides, you perform in vitro transcription. However, even though all of your controls work, no mRNA is created from your DNA fragment. Working backward, you note that your DNA preparation removed approximately 250 base pairs from the 5' end of the gene. The most likely explanation is that during DNA preparation
the promoter was removed.
Which of the following is a reason why ATP hydrolysis has a negative ΔG0?
the removal of the phosphate is energetically favorable FEEDBACK: 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.
Gene expression always involves
transcription
(Q010) Archaea and bacteria are two separate domains of prokaryotes that were distinguished by examining
their DNA sequences.
What is the role of activated carriers in cells?
they capture energy from energy releasing reactions and transfer it to other reactions,. FEEDBACK: 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.
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
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- The genetic code consists of three consecutive bases and is read in a nonoverlapping fashion. That is, the nucleotides for one triplet are not the part of the next triplet.
The information in an mRNA molecule is converted into protein sequence using
three consecutive bases, with no overlap between triplets.
What is a function of the nucleolus?
to assemble ribosomal RNA and proteins into ribosomes
The phosphates are held together by ____________ ____________ bonds
unstable phosphate
In eukaryotes, where do transcription regulators bind?
upstream, downstream, or within the genes they control
Many organisms, including plants, have slick coverings made of ____________ , which provide both protection and waterproofing.
waxes
(Q009) Ionic bonds are ___________ than covalent bonds and are ___________ common in cells.
weaker; less
Ionic bonds are _____________ than covalent bonds and are ____________ common in cells.
weaker; less
In mRNA do several different codons codes for the same amino acid in some cases
yes
In mRNA molecules do all codons contain three nucleotides
yes
(Q010) 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 FEEDBACK: The value of the free-energy change of a reaction, ΔG, is dependent upon the concentration of reactants and products, as well as the temperature of the system. ΔG0 is the standard free-energy change at standard temperature and concentrations to allow comparison of different reactions.
(Q011) What is the relationship between ΔG and ΔG0?
ΔG0 is the free-energy change at standard temperature and concentrations.
(Q004) 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?
α helix (D)
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.
