cell phys exam 2
37. The Na+/ K+ ATPase is responsible for maintaining the gradients of these ions across the cell membrane (and helping establish the membrane potential). It does so by pumping; a. 3 Na+ molecules out of the cell for each 2 K+ molecules brought in b. 2 Na+ molecules out of the cell for each 3 K+ molecules brought in c. 2 K+ molecules out of the cell for each 3 Na+ molecules brought in d. The Na+/ K+ ATPase is not a pump, it is an ion channel
a.
1. RNA polymerases I, II and III respectively transcribe: a. mRNA, tRNA, rRNA b. mRNA, rRNA, tRNA c. rRNA, tRNA, mRNA d. rRNA, mRNA, tRNA
d.
3. Transcription in bacteria differs from transcription in a eucaryotic cell because a. RNA polymerase (along with its sigma subunit) can initiate transcription on its own b. RNA polymerase (along with its sigma subunit) requires the general transcription factors to assemble at the promoter before polymerase can begin transcription c. The sigma subunit must associate with the appropriate type of RNA polymerase to produce mRNAs d. Bacterial RNA polymerase must be methylated at its C-terminal tail
a.
30. Introns and transposons tend to assist in the evolution of new genes. a. True b. False
a.
16. A binds to its operator ______ tightly than B binds to its operator. a. More b. Less
a.
26. Genes involved in amino acid synthesis (A) vs genes involved in development (B) a. A b. B
a.
29. To determine the most functionally important regions of the human genome (i.e., what makes us unique), which species would be more useful for comparison? a. Chimpanzee (diverged from humans 5 million years ago) b. Gorilla (diverged from humans 10 million years ago) c. Orangutan (diverged from humans 30 million years ago)
a.
35. Membranes are enlarged by the insertion of new phospholipids into one side of the membrane. Which side? a. Cytoplasmic b. Noncytoplasmic
a.
7. You have identified a protein factor that when added to in vitro protein synthesis reaction increases the incorporation of 35S-methionine from 4 pmoles/minute to 8 pmoles/min. When you centrifuge these reactions and measure polyribosomes and free ribosomes, you observe that more of the ribosomes are present as polyribosomes for the reactions that contain your stimulatory factor. Which explanation is consistent with this result? a. Your factor binds to the small subunit to promote translation initiation b. Your factor binds to the large subunit to promote translation termination c. Your factor binds to the ribosome to decrease the rate of elongation d. Your factor binds to the ribosome to increase the rate of elongation
a.
33. How do cells change the orientation of phospholipids in the plasma membrane? a. By increasing the fluidity of the lipid bilayer. b. By using enzymes which rotate phospholipids through the bilayer (flippases). c. By budding and fusing of membrane vesicles. d. By temporary breaks in the bilayer that release the phospholipids from the membrane. e. The orientation of membrane phospholipids cannot be changed.
b
34. You want to amplify the DNA between the two stretches of sequence shown below. Of the listed primer pairs, choose the correct pair that will allow you to amplify the DNA by PCR. 5'-CTGGACGAAA----TGTAATGGTT-3' 3'-GACCTGCTTT----ACATTACCAA-5' a. 5'-CTGGACGAAA-3' and 5'-TGTAATGGTT-3' b. 5'-CTGGACGAAA-3' and 5'-AACCATTACA-3' c. 5'-TTTCGTCCAG-3' and 5'-TGTAATGGTT-3' d. 5'-GACCTGCTTT-3' and 5'-ACATTACCAA-3'
b
13. The gene regulatory protein that binds to site B is ____ that also binds _______ a. A repressor, trehalose b. A repressor, glucose c. An activator, trehalose d. An activator, glucose
b.
15. A pseudogene represents a duplication of a functional gene that has diverged and is expressed by the cell to perform a new function. a. True b. False
b.
17. A is a _______ activator of transcription than B a. Stronger b. Weaker
b.
19. Which of the following steps in protein synthesis require ATP hydrolysis? a. Joining two amino acids together on the ribosome. b. Attaching an amino acid to a tRNA. c. Binding of tRNA to the ribosome. d. Binding of the ribosome to mRNA. e. Base-pairing of codon and anticodon
b.
2. The distinct characteristics of different cell types in a multicellular organism are produced mainly by the differential regulation in the: a. translation of mRNA b. transcription of genes transcribed by RNA polymerase II. c. transcription of housekeeping genes. d. inactivation of specific genes. e. packing of DNA into nucleosomes in some cells and not others.
b.
22. Eukaryotic RNA polymerase II alters its conformation after binding to a promoter as it makes the transition from DNA-binding to the transcription of RNA. RNAP II is modified at it's (C or N)-terminal domain by (methylation or phosphorylation). a. C, methylation b. C, phosphorylation c. N, methylation d. N, phosphorylation
b.
24. A major reason why DNA rather than RNA is used for the storage of genetic information is a. DNA base pairing is significantly more stable than RNA base pairing b. DNA is more stable than RNA c. Only DNA can form antiparallel double strands d. There is no enzyme that can make a complementary copy of RNA
b.
25. Genes involved in sexual reproduction (A) vs. genes involved in translation (B) a. A b. B
b.
27. The DNA of introns is more highly conserved than the DNA of exons a. True b. False
b.
28. Most genome alterations and mutations have a. Positive consequences for organisms b. Neutral consequences for organisms c. Negative consequences for organisms
b.
36. 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. Increase the length of the hydrocarbon tails in its membrane phospholipids. b. Increase the proportion of unsaturated hydrocarbon tails in its membrane phospholipids (i.e., more double bonds). c. Decrease the proportion of unsaturated hydrocarbon tails in its membrane phospholipids (i.e., fewer double bonds). d. Decrease the amount of cholesterol in the membrane
b.
41. Ion channels a. Allow cells to concentrate ions against a concentration gradient b. Can be regulated by a membrane voltage, a specific ligand or a mechanical stress c. Are nonspecific for Na+, K+, or Ca++ d. Are examples of peripheral membrane proteins
b.
5. The bold sequences (TTGACA and TATATT) represent a. TATA boxes recognized by RNAP II b. -35 and -10 boxes recognized by the sigma factor of RNAP c. Binding sites for general transcription factors d. Binding sites for the small subunit of the ribosome
b.
6. If transcription starts at the arrow, the sequence of the transcribed RNA will be: a. 5'-AGGTC...-3' b. 5'-AGGUC...-3' c. 5'-TCCAG...-3' d. 5'-UCCAG...-3
b.
9. Which of the following statements regarding lipid membranes is true? a. Phospholipids will spontaneously form liposomes in nonpolar solvents. b. Membrane lipids move laterally within their own layer. c. Membrane lipids spontaneously flip from one layer of the bilayer to the other. d. The preferred form of a lipid bilayer in water is a flat sheet with exposed edges.
b.
12. Given that mutant 1 has sites A-B+, the gene regulatory protein that binds to site A is ____ that also binds _______ a. A repressor, trehalose b. A repressor, glucose c. An activator, trehalose d. An activator, glucose
c.
18. C is able to prevent activation by ________ a. A only b. B only c. Both A and B
c.
20. Which of the following statements is correct? a. Ribosomes are large RNA structures composed solely of rRNA. b. Ribosomes are synthesized entirely in the cytoplasm. c. rRNA contains the catalytic activity that joins amino acids together. d. A ribosome consists of two equally sized subunits. e. A ribosome binds one tRNA at a time.
c.
21. A poison added to an in vitro translation mixture containing mRNA molecules with the sequence 5'-AUGAAAAAAAAAAAAUAA-3' has the following effect: the only product made is a Met-Lys-Lys-Lys-Lys peptide that remains attached to the ribosome. What is the most likely way in which the poison acts to inhibit protein synthesis? a. It inhibits binding of the small subunit of the ribosome to mRNA. b. It inhibits peptidyl transferase activity. c. It inhibits movement of the small subunit relative to the large subunit. d. It inhibits release factor. e. It mimics release factor.
c.
23. What is the most likely cause of this variation in protein sequence? a. A mutation in the spliceosome that leads to inaccurate RNA splicing. b. A mutation in the anticodon of the isoleucine tRNA (tRNAIle). c. A mutation in the isoleucyl-tRNA synthetase that decreases its ability to distinguish between different amino acids. d. A mutation in the isoleucyl-tRNA synthetase that decreases its ability to distinguish between different tRNA molecules. e. A mutation in small subunit of the ribosome that allows binding of incorrect tRNA molecules to the A-site.
c.
31. The differences between humans and chimps are largely due to: a. The larger number of genes in the human genome b. Unique genes found only in the human genome c. Differences in gene regulation d. Unique genes found only in the chimp genome
c.
32. A large number of different proteins can be expressed from a single eukaryotic gene due to a. Allosteric modifications b. Protein degradation c. Alternative splicing d. Synteny
c.
43. Four samples of cells have membranes containing a uniform distribution of a fluorescently labeled phospholipid (sample 1) and three fluorescently labeled membrane proteins X, Y, and Z (samples 2-4), respectively. An intense beam of light is shone on each sample. The light beam destroys the fluorescent label in the illuminated area, but the intensity of fluorescence in the area recovers over time, as bleached molecules diffuse away and unbleached molecules diffuse in. The results of this experiment are shown in below. Which of the following interpretations is INCONSISTENT with these results? a. A. X is a small freely diffusing protein. b. B. Y is a large freely diffusing protein. c. C. X and Y are part of the same large protein complex. d. D. Z is bound to a component of the cell cortex or cytoskeleton and is not free to diffuse.
c.
10. The concentration of a particular protein X in a normal human cell rises gradually from a low point, immediately after cell division, to a high point, just before cell division, and then drops sharply. The level of its mRNA in the cell remains fairly constant throughout this time. Protein X is required for cell growth and survival, but the drop in its level just before cell division is essential for division to proceed. You have isolated a line of human cells that grow in size in culture but cannot divide, and on analyzing these mutants, you find that levels of X protein do not decrease. Which of the following mutations could explain these results? a. A mutation that results in the loss of an enzyme that adds a ubiquitin tag to the protein. b. a mutation in gene X that results in the loss of polyA addition to its mRNA c. a mutation in gene X that changes the sequence that encodes sites at which ubiquitin can be attached to the protein d. Both A and C
d.
14. What is the "genotype" of mutant 3? a. (A+ B+) b. (A- B+) c. (A- B-) d. either b or c
d.
38. The membrane potential of a typical animal cell favors the inward flux of: a. Water b. Cl- c. ATP d. Ca2+.
d.
39. In nerve cell signaling the action potential travels in one direction because: a. the Na+/ K+ pump restores the concentrations of Na+ and K+ to their original levels. b. the K+ leak channels allow K+ to flow out, restoring the membrane to the resting potential. c. depolarization of the membrane causes voltage-gated K+ channels to open. d. voltage-gated Na+ channels adopt a transitory inactive conformation after being opened. e. voltage-gated Na+ channels spend less time in the open conformation when the membrane returns to the resting potential
d.
4. What is a riboswitch? (a) A microRNA that inhibits RNAP synthesis. (b) An RNA that can adopt different conformations upon binding a ligand like a metabolite. (c) An RNA that can control it's own synthesis or translation. (d) Both B and C.
d.
40. The most abundant intracellular cation is: a. Na+. b. Ca2+. c. H+. d. K+.
d.
42. You have an oligonucleotide probe that hybridizes to part of gene A from a eucaryotic cell. Choose whether a cDNA library or a genomic DNA library will be more appropriate to use for the following applications. A) To study the promoter of a gene A. B) To express gene A in bacteria to produce lots of protein A. a. A; cDNA library, B; cDNA library b. A; genomic library, B; genomic library c. A; cDNA library,B; genomic library d. A; genomic library, B; cDNA library
d.
8. The lipid bilayer is held together mainly by: a. covalent bonding between membrane lipids. b. hydrogen-bonding between the phospholipid tails. c. repulsion between the hydrophobic phospholipid tails and water. d. covalent bonding between the ends of phospholipid tails in opposite layers e. hydrogen-bonding between the head groups of phospholipids.
e.
Which of the following conclusions can be drawn from your data? a. BRF2 is a repressor of BRF1. b. BRF2 and HHF are required for the specific pattern of nucleosome positions over the BRF1 upstream region. c. The specific pattern of nucleosome positioning over the BRF1 upstream region is required for BRF1 repression. d. BRF2 protein must interact with histone H4. e. Both a and b
e.
