Cell Bio Final 2

Front 1

1. Which of the following statements about biological membranes is false?

Back 1

b. They are formed primarily of lipid and carbohydrate

Front 2

2. Which of the following is least permeable through a lipid bilayer?

Back 2

d. Na+

Front 3

3. Which one of the following statements about the diffusion of lipids and proteins in membranes is NOT true?

Back 3

d. Lipids diffuse across and in the plane of the membrane at equal rates

Front 4

4. Which of the following about composition of membranes is true?

Back 4

c. The inner and outer membranes of mitochondria have different protein composition

Front 5

5. If you were to inject a squid giant axon with a tiny folume of solution containing 0.1 M NaCl and 0.1 M KCl in which both Na+ and K+ were radioactive, after placing that axon into a seawater medium, which of the radioactive ions would you expect to appear most rapidly in the medium when the neuron remained at rest?

Back 5

a. Na+

Front 6

6. Doing the same procedure as in 5 above, which of the radioactive ions would you expect to appear most rapidly in the medium after the axon had been stimulated?

Back 6

b. K+

Front 7

7. Acetylcholine is made in the cytosol and then transported into synaptic vesicles. When synaptic vesicles are isolated from neurons, they can take up additional acetylcholine added to the solution in which they are suspended, but only when ATP is present. Na+ ions are not required for the uptake, but, curiously, raising the pH of the solution in which the synaptic vesicles are suspended increases the rate of uptake. Furthermore, transport is inhibited when drugs are added that make the membrane permeable to H+ ions. A mechanism which would fit these data is

Back 7

d. ATP is used to maintain a H+ gradient [higher in vesicle] for an antiport action for H+/acetylcholine membrane reverse transport

Front 8

8. Transport may be active or passive. Transport by carrier proteins is always positive whereas transport by channel proteins is always passive.

Back 8

b. false

Front 9

9. A symporter would function as an antiporter if its orientation in the membrane were reversed – i.e. the portion of the protein normally cytosolic were noncytosolic (facing toward the outside of the cell).

Back 9

b. false

Front 10

10. The membrane potential can change from movements of charge that leave ion concentrations practically unaffected but result in a slight discrepancy in the number of positive and negative ions on either side of the membrane. This slight concentration is enough to affect a change in membrane potential, e.g. versus requiring a high difference in ion concentration with large numbers of ion migration.

Back 10

a. true

Front 11

11. Upon stimulation of a nerve cell, resultant processes that limit the entry of Na+ ions are: (1) the Na+ concentration reaches equilibrium across the membrane or the membrane potential reaches the Na+ equilibrium potential (2) the Na+ channels are inactivated and cannot reopen until the original resting potential have been restored.

Back 11

a. true

Front 12

12. The basic structure of biological membranes is determined by the ____, but their specific functions are carried out largely by ____.

Back 12

e. lipids, proteins

Front 13

13. Cells use various methods to restrict proteins to specific regions of the plasma membrane; however, the lipids are still free to move around these restrictions, like water flowing around rocks. The methods used by the cell to restrict proteins to specific areas of the membrane include all of the following EXCEPT

Back 13

d. insertion of active transport channels

Front 14

14. That particular event which happens at axon terminals and which causes vesicles containing stored neurotransmitter to migrate toward the membrane and release their contents extracellularly is

Back 14

d. opening of a voltage-gated Ca++ channel

Front 15

15. That common intermediate of lipid and carbohydrate metabolism which enters mitochondria and is further oxidized in the Kreb’s cycle to yield ATP energy molecules is

Back 15

c. acetyl-CoA

Front 16

16. In the absence of oxygen, pyruvate can be metabolized to _________ in order to ___________

Back 16

e. a and c

Front 17

17. In glycolysis in absence of oxygen, the prokaryotic equivalent of eukaryotic pyruvate is

Back 17

d. ethanol

Front 18

18. If a mole of triacylglycerols were completely oxidized, it would yield (more/fewer) ATPs than a mole of glucose that was completely oxidized.

Back 18

a. more

Front 19

19. If one had isolated a specific DNA and were attempting to integrate it into a plasmid vector, one would be assisted by

Back 19

c. Eco R1, Not 1 or Hind III

Front 20

20. In order for a plasmid to serve as a vector, it should include DNA coding for

Back 20

e. a and b

Front 21

21. Looking at the dideoxy experiment on the

Back 21

b. ATGTCAGTCCAG

Front 22

22. Almost all cells in an individual animal contain identical genomes. In an experiment, a tissue composed of multiple cell types is fixed and subjected to in situ hybridization with a DNA probe to a particular gene. This hybridization signal is found to be more concentrated in some cells than others. This is most likely reason is due to the fact that

Back 22

d. The DNA probe combined with mRNA as well as DNA and the mRNA was more highly expressed in some cells

Front 23

23. By far, the most important advantage of cDNA clones over genomic clones is that they contain the complete coding sequence of all of an organism’s genes without intervening introns.

Back 23

b. false

Front 24

24. A reporter gene is best defined as

Back 24

b. a gene whose activity can be easily monitored

Front 25

25. If one were interested in studying the phenotype of a series of cells with varying gene expression, one would compare

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b. c-DNA of the cells

Front 26

26. Knockout genes are those which

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d. are never expressed

Front 27

27. Membrane-bound and free ribosomes, which are structurally and functionally identical, differ only in the proteins they happen to be making at a particular time.

Back 27

a. true

Front 28

28. To avoid the inevitable congestion that would occur if two-way traffic through a single pore were allowed, nuclear pore complexes appear to be specialized so that some mediate import while others mediate export.

Back 28

FALSE

Front 29

29. The most prolific organelle in cells is

Back 29

b. mitochondria

Front 30

30. Nuclear localization signals are attached during synthesis in the

Back 30

a. cytoplasm

Front 31

31. Nuclear localization signals (are/are not) cleaved off after transport into the nucleus as are signal sequences for import into other organelles because during mitosis, the nucleus disassembles and then reassembles in the new daughter cells and the proteins need to be directed toward their specific locations in the new cells.

Back 31

b. are not

Front 32

32. The signal peptide for ER, when it emerges from the ribosome, binds to a site on the ribosomal translation complex causing the rate of protein synthesis to rapidly increase so that the entire protein is completely synthesized before reaching the ER where it is integrated through the membrane

Back 32

b. false

Front 33

33. If one observed the formation of Clathrin-coated vesicles budding from eukaryotic plasma membranes, what would you expect to observe if adaptins were not available?

Back 33

b. false

Front 34

34. SNAREs exist as complementary partners (v-SNARE and t-SNARE) that carry out membrane fusions between appropriate sesicles and their target membranes. In an experiment, however, you observe fusions of identical membraned vesicles. What would explain this phenomenon?

Back 34

c. the vesicles would be empty and have not cargo

Front 35

35. Viruses are the ultimate scavengers—a necessary consequence of their small genomes. These so-called enveloped viruses gain access to the cytosol by fusing with a cell membrane. Why do you suppose that each of these viruses encodes its own special fusion protein, rather than making use of a cell’s SNAREs?

Back 35

d. the vesicles had both v and t-SNARES (were both directed and targeted)

Front 36

36. The one strict requirement for a protein to exit from the Er is

Back 36

b. the SNAREs are on the cytosolic side the membrane, inaccessible to viruses

Front 37

37. All of the glycoproteins and glycolipids in the plasma membrane have their oligosaccharide chain facing the outside of the cell. Following this logic as all carbohydrate moieties are attached in the Golgi, all glycoproteins and glycolipids of intracellular membranes are facing

Back 37

e. that it be correctly synthesized and folded

Front 38

38. The delivery of proteins to the interior of the nucleus differs from that of delivery to other membrane-bound organelles in that

Back 38

a. the nuclear proteins are delivered in their 3D configuration across the membrane

Front 39

39 LDL receptors are released from lysosomes and recycled to the cell membrane.

Back 39

a. true

Front 40

40. There is no fundamental distinction between signaling molecules that bind to cell-surface receptors and those that bind to intra-cellular receptors.

Back 40

b. false

Front 41

41. How do you expect the activity of a G protein would be affected by a mutation that caused its affinity for GDP to be reduced without significantly changing its affinity for GTP? The mutant would show

Back 41

b. more activity

Front 42

42. How is an IP3-triggered Ca++ response terminated?

Back 42

d. by removing phosphates from IP3

Front 43

43. In contrast to the more direct signaling pathways used by nuclear receptors, catalytic cascades of intracellular mediators provide numerous opportunities for amplifying the responses to extracellular signals.

Back 43

a. true

Front 44

44. Once v-Snares bind to t-Snares,

Back 44

c. they remain dockted until activated to fuse by some signal

Front 45

45. Proteins totally synthesized in the cytoplasm are targeted toward all of the following EXCEPT

Back 45

c. lysosomes

Front 46

46. Two protein kinases, PK1 and PK2, work sequentially in a signal transduction pathway. You create cells that contain

Back 46

a. PK1 activates PK2

Front 47

47, 48. During the mating process, yeast cells respond to pheromones that are secreted from other cells. These pheromones bind to G-protein-linked receptors on the surface of the responding yeast cell and lead to activation of G proteins inside the cell. When a wild-type yeast cell senses the pheromone, its cellular physiology changes in preparation for mating: the cell stops growing until a mating partner is found. If yeast cells do not undergo the appropriate cellular responses upon sensation of pheromone, they are considered sterile. Yeast cells that are defective in one or more components of the G protein have characteristic phenotypes in the absence and presence of the pheromone, which are listed below.

Back 47

Gbg activates the mating response but is inhibited when bound by Ga.

Back 48

Gbg activates the mating response but is inhibited when bound by Ga.

Front 49

49, 50. Acetylcholine acts at a G-protein-linked receptor on heart muscle to make the heart beat

Back 49

A high concentration of a non-hydrolyzable analog of GTP. Modification of the acetylcholine-receptor-linked G protein a subunit by cholera toxin.

Back 50

A high concentration of a non-hydrolyzable analog of GTP. Modification of the acetylcholine-receptor-linked G protein a subunit by cholera toxin.