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Cell Bio Exam 2
1. Which of the following molecules does not contain a fatty acid tail? (a) Phosphatidylcholine (b) A glycolipid (c)
Phosphatidylserine (d) SDS
2. Which of the following statements is true? (a) Phospholipids will spontaneously form liposomes in polar solvents. (b) In
eucaryotes, all membrane-enclosed intracellular compartments are surrounded by one lipid bilayer. (c) Membrane lipids do not
diffuse within the plane of the membrane. (d) Membrane lipids frequently flip-flop between one monolayer and the other.
3. You got a cell line with no name, but it says that this cell line forms coated pits but vesicle budding and the removal of coat
proteins don’t happen. Which of the following proteins might be lacking in this cell line?(a) clathrin (b) Rab (c) dynamin (d) adaptin
4. Bacterial porin proteins form large, barrel-like channels in the membrane. Which of the following is true about these channels?
(a) They are made primarily of coiled-coil structure. (b) They are made primarily of β-sheets. (c) They can form narrow channels.
(d) They have hydrophobic amino acids on every seventh position.
5. The endothelial cells found closest to the site of an infection express proteins called _____, which binds to a particular
oligosaccharide that is presented on the surface of a target cell. (a) antibody (b) lectin (c) cholesterol (d) sphingolipid
True or False?
6. The extracellular side of the integral membrane proteins is often glycosylated. (a) True (b) False 7. Cholesterol equally locates to the outer and inner leaflets of the plasma membrane. (a) True (b) False 8. Which of the following proteins is a GTP binding protein? (a) v-SNARE (b) t-SNARE (c) adaptin (d) Rab
9. Transmembrane proteins cross the plasma membrane as an unfolded polypeptide. (a)True (b)False
10. !Membrane!proteins!that!pump!ions!in!and!out!of!the!cell!are!classified!as!enzymes.!(a) True (b) False 11. A symport would function as an antiport if its orientation in the membrane were reversed. (a) True (b) False 12. The lateral motility of membrane proteins can be restricted by gap junctions. (a) True (b) False
1 3. An electrical signal is converted into a chemical signal at the synapse by a stress gated chloride channel. (a) True (b)
False
14. The resting membrane potential of animal cells is always 60 mV. (a) True (b) False 15. A voltage-gated Na+ channel adopts three alternative conformations. (a) True (b) False 16. Tight junction permits selective ion transport. (a) True (b) False 17. Calcium channel is open during hyperpolarization step. (a) True (b) False
1 8. !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!Triton!X<100.!(a) True (b) False
19. 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
20. !Which of the following membrane lipids does not contain a fatty acid tail? (a) Phosphatidylcholine (b) A glycolipid (c)
Phosphatidylserine (d) Cholesterol
21. Which of the following is required for the secretion of neurotransmitters in response to an action potential?
(a). neurotransmitter receptors (b). Na
pumps (c). voltage-gated K
channels (d). voltage-gated Ca
2+ channels
22. Transporters, in contrast to channels, work by _____. (a). specific binding to solutes (b). nonspecific binding to
solutes (c).filtering solutes by charge (d).filtering solutes by size
23. Which of the following best describes the behavior of a gated channel? (a)It stays open continuously when
stimulated. (b) It opens more frequently in response to a given stimulus. (c)It opens more widely as the stimulus
becomes stronger. (d)It remains closed if unstimulated.
24. The stimulation of auditory nerves depends on the opening and closing of channels in the auditory hair cells.
Which type of gating mechanism do these cells use? (a)voltage-gated (b)extracellular ligand-gated (c)intracellular
ligand-gated (d) stress-gated
25. Active transport requires the input of energy into a system so as to move solutes against their electrochemical
and concentration gradients. Which of the following is one of the common ways to perform active transport? (a)
Na
coupled (b) Cl
- coupled (c) SO 4
2 -
3 -
26 - 28. Assume that this membrane vesicle is in the cytoplasm of a cell.
26. Proteins destined to go the extracellular space can interact with: (a) N-terminus (b) C-terminus
27. This membrane vesicle will undergo fusion with the plasma membrane. After the event of fusion, proteins in the
cytoplasmic side can interact with: (a) N-terminus (b) C-terminus
28. This membrane vesicle will undergo fusion with the plasma membrane. After the event of fusion, which
membrane leaflet will face cytoplasmic side? (a) solid line (b) broken line
29. You are interested in Fuzzy, a soluble protein that functions within the ER lumen. Given that information, which
of the following statement must be false?
(a) Fuzzy has a N-terminal signal sequence that binds to SRP. (b) Multiple ribosomes can be bound to the mRNA
encoding Fuzzy during translation. (c) Fuzzy does not contain a hydrophobic stop-transfer sequence. (d) Even after
the signal sequence from Fuzzy has been cleaved, the signal peptide will still associate with Fuzzy in the ER
membrane.
30. Figure Q 15 - 19 shows the organization of a protein that normally resides in the plasma membrane. The boxes
labeled 1 and 2 represent membrane-spanning sequences and the arrow represents a site of action of signal
peptidase. Given this diagram, which of the following statements must be true?
Figure Q15- 19
(a) The N-terminus of this protein is cytoplasmic. (b) The C-terminus of this protein is cytoplasmic. (c) The mature
version of this protein will span the membrane twice, with both the N and C termini in the cytoplasm. (d) None of
the above.
31. We can test the relative permeability of a phospholipid bilayer by using a synthetic membrane that does not contain any
protein components. Some uncharged, polar molecules are found to diffuse freely across these membranes, to varying degrees.
Which of the following has the lowest rate of diffusion across an artificial membrane? (a) sucrose (b) hydrogen peroxide
(c) glycerol (d) ethanol
32. Which mechanism is not true for channels? (a) specific binding to solutes (b) a gating mechanism (c) filtering solutes by
charge (d) filtering solutes by size
33. If K
channels are opened in a cell that was previously at rest, how will the resting membrane potential be affected?
(a) The membrane potential is not affected by K
. (b) It becomes hyperpolarized. (c) It becomes depolarized. (d) It is
permanently reset.
34. Which of the following is required for the secretion of neurotransmitters in response to an action potential? (a) NCX
(Sodium Calcium Exchanger (b) Na
- K
pumps (c) neurotransmitter-gated Ca
channels (d) voltage-gated Ca
channels
35. Which of the following statements about the endoplasmic reticulum (ER) is false? (a) The smooth ER is the major site for
new membrane phospholipid synthesis in the cell. (b) Proteins to be delivered to the ER lumen are synthesized on the rough
ER. (c) The ER membrane is not contiguous with the Golgi complex. (d) The proteins in the lumen of ER will be easily reduced.
36. Which of the following statements is true? (a) The signal sequences on mitochondrial proteins are usually C- terminal. (b)
Most mitochondrial proteins are imported from the cytosol. (c) Chaperone proteins in the mitochondria discourage the
movement of proteins across the outer and inner mitochondrial membranes. (d) Mitochondrial proteins cross the membrane in
their native, folded state.
37. After isolating the rough endoplasmic reticulum from the rest of the cytoplasm, you purify the RNAs attached to it. Which of
the following proteins do you expect the RNA from the rough endoplasmic reticulum to encode?
(a) soluble cytoplasmic proteins (b) nuclear proteins (c) proteins with the signal peptide (d) none of the above
38. Which of the following choices reflects the appropriate order through which a membrane receptor protein destined to travel a
lysosome? (a) plasma membrane → Golgi → lysosome (b) plasma membrane → endosome → lysosome (c) ER → plasma
membrane → lysosome (d) Golgi → plasma membrane → lysosome
39. Which of the following statements about vesicle budding from the Golgi is true?
(a) Clathrin molecules are important for binding to and selecting cargos for transport. (b) Adaptins interact with the cargo. (c)
Clathrin molecules persistently associate with the vesicle even after the vesicular budding is completed. (d) Clathrin molecules
act both at the cytosolic surface of the Golgi membrane and the plasma membrane.
40. What is the role of the nuclear localization sequence in a nuclear protein?
(a) It is bound by cytoplasmic proteins that direct the nuclear protein to the nuclear pore.
(b) It is a hydrophobic sequence that enables the protein to enter the nuclear membranes.
(c) It aids in protein unfolding so that the protein can thread through nuclear pores.
(d) It prevents the protein from diffusing out of the nucleus through nuclear pores.
N 1 2 C
