Bil 255, Cell Biology - Fall Semester 2007 - 2nd Examination - Form 1


1. You are studying membrane transport of a newly discovered small molecule. You find that this molecule always moves from a region of lower concentration to a region of higher concentration. You find that as you increase the concentration difference between the inside and outside of the cell, the rate of movement of the molecule across the membrane increases. However, as the concentration difference increases to large values, the rate of movement across the membrane appears to reach a limiting maximum value. What is the most likely mechanism for the membrane transport?

1) facilitated diffusion.
2) active transport
3) Fick's law thermal diffusion.
4) Air France

Correct Answer is: 2


2. Which of the following has the highest release of free energy upon conversion to its oxidized form?

1) NADH
2) FADH2

Correct Answer is: 1


3. Which of the following shuttles is most important in bring reducing power into the mitochondria of nerve cells in the brain?

1) galactose-inosine
2) glycerol-phosphate.
3) kennedy-laguardia.
4) pyruvate-lactate.
5) malate-aspartate.

Correct Answer is: 2


4. Suppose that you measure a resting membrane potential of -88 mV in a human nerve cell at 40 degrees C. If you now cool the patient down to 20 degrees C, what membrane potential will you measure in the same nerve cell?

1) Membrane potential will stay at -88 mV
2) -44.00 mV
3) -82.37 mV
4) -94.01 mV

Correct Answer is: 3


5. Which of the following best describes the distribution of lecithin between the exoplasmic and cytosolic sides of cell membranes ?

1) Most lecithin is on the exoplasmic side of cell membranes
2) Most lecithin is on the cytosolic side of cell membranes
3) Lecithin is distributed equally on both sides of cell membranes.

Correct Answer is: 1


6. What characteristic of lipids makes them more saturated?

1) more cholesterol and less phospholipid
2) phospholipid molecules are closer together.
3) fewer double bonds in the hydrophobic tails.
4) more phospholipid and less cholesterol
5) increased number of atoms in the polar head.

Correct Answer is: 3


7. Which of the following best describes the method by which GTP is synthesized by the citric acid cycle?

1) chemiosmosis
2) Hatch-Slack reactions.
3) pyruvate dehydrogenase complex.
4) GTP is not generated in the reactions of the citric acid cycle.

Correct Answer is: 3 (ERROR - NO CORRECT ANSWER)


8. People with type A blood have glycolipids and glycoproteins which have an carbohydrate called __________ added to the basic type O carbohydrate chain. (Fill in the blank)

1) D-glycomesmerate
2) spectrin.
3) melmolose
4) phosophatidylinositol.
5) N-Acetylgalactosamine.

Correct Answer is: 5


9. True or False: In humans, fructose is transported into the cells of the intestinal epithelium by cotransport with sodium

1) True
2) False

Correct Answer is: 2


10. As changes in membrane potential take place between the start and the peak of an action potential, what happens to the ratio (gCl/gK)

1) decreases
2) increases.
3) stays the same.

Correct Answer is: 1


11. Observations of the ionic nature of proteins within cells lead us to believe that:

1) Most proteins are uncharged at physiological pH.
2) Most proteins are positively charged at physiological pH.
3) Most proteins are negatively charged at physiological pH.

Correct Answer is: 3


12. Glycophorin A has _______ transmembrane alpha-helices.

1) 1
2) 2
3) 4
4) 6

Correct Answer is: 1


13. Suppose that we discover a new type of cell. It is shown that only one ion, with charge +3, can freely diffuse across this cell's membrane. The concentration of this ion is 10 mM inside the cell and 10 mM outside the cell. What can we say about the membrane potential?

1) The inside of the cell must be have a negative membrane potential with respect to the outside of the cell.
2) The inside of the cell must be have a positive membrane potential with respect to the outside of the cell.
3) The membrane potential is zero.

Correct Answer is: 3


14. Which of the following is correct concerning phosphatidyl inositol?

1) It is a lipid, found mostly on the cytosol side of animal cell membranes.
2) It is a glycolipid, found mostly on the exterior surface of animal cell membranes.
3) It is a form of cholesterol.
4) Another name for this molecule is lecithin.

Correct Answer is: 1


15. Suppose that the membrane potential inside a cell is -62 mV at 37 degrees C. There is only one permeable ion. Magically, we manage to increase concentrations of the single permeable ion, inside and outside, by ten times their original values. What happens to the membrane potential?

1) It becomes a larger negative value.
2) It becomes a smaller, but still negative, value.
3) It changes polarity and becomes a positive value.
4) The membrane potential does not change.

Correct Answer is: 4


16. Animal cells use sodium pumps to remove sodium from the inside of cells. This process takes energy supplied by ATP. What ion do plant cells substitute for sodium in this process of active transport from the inside to outside of the cell?

1) hydrogen ions
2) potassium ions.
3) magnesium ions.
4) Plants pump sodium, just like animals.

Correct Answer is: 1


17. Which of the following shuttles is most important in bring reducing power into the mitochondria of the human kidney?

1) galactose-inosine
2) glycerol-phosphate.
3) kennedy-laguardia.
4) pyruvate-lactate.
5) malate-aspartate.

Correct Answer is: 5


18. True or False: Cholesterol is a phospholipid.

1) True.
2) False.

Correct Answer is: 2


19. Which of the following is a allosteric enzyme which shows negative cooperativity?

1) Hexokinase.
2) The enzyme that catalyzes the conversion of glucose to glucose-6-phosphate.
3) The enzyme that catalyzes the conversion of fructose 1,6 biphosphate to dihydroxyacetone phosphate and glyceraldehyde 3-phosphate.
4) The enzyme that catalyzes the conversion of glyceraldehyde 3-phosphate to 1,3-biphosphoglycerate.

Correct Answer is: 4


20. Which of the following best describes the characteristics of glucose movement across the side of intestinal epithelial cells which faces the intestinal lumen?

1) active transport of glucose with energy for the transport supplied by GTP.
2) cotransport with potassium, with the glucose moving from higher glucose concentrations in the intestinal lumen to lower glucose concentrations in cytosol of the intestinal epithelial cells.
3) cotransport with potassium, with the glucose moving from lower glucose concentrations in the intestinal lumen to higher glucose concentrations in cytosol of the intestinal epithelial cells.
4) cotransport with sodium, with the glucose moving from higher glucose concentrations in the intestinal lumen to lower glucose concentrations in cytosol of the intestinal epithelial cells.
5) cotransport with sodium, with the glucose moving from lower glucose concentrations in the intestinal lumen to higher glucose concentrations in cytosol of the intestinal epithelial cells.

Correct Answer is: 5


21. With respect to the Na/K ATPase pump:

1) For each ATP used, 2 sodium ions are pumped out of the cell and 2 potassium ions are pumped in.
2) For each ATP used, 3 sodium ions are pumped out of the cell and 2 potassium ions are pumped in.
3) For each ATP used, 2 sodium ions are pumped out of the cell and 3 potassium ions are pumped in.
4) For every 3 ATP used, 3 sodium ions are pumped out of the cell and 2 potassium ions are pumped in.
5) For every 3 ATP used, 2 sodium ions are pumped out of the cell and 3 potassium ions are pumped in.

Correct Answer is: 2


22. Which of the following best describes the distribution of cephalin between the exoplasmic and cytosolic sides of cell membranes ?

1) Most cephalin is on the exoplasmic side of cell membranes
2) Most cephalin is on the cytosolic side of cell membranes
3) Cephalin is distributed equally on both sides of cell membranes.

Correct Answer is: 2


23. Which is most accurate concerning membrane phospholipids of animal cells?

1) Have significantly saturated hydrophobic chains with 16 to 20 carbons.
2) Have significantly saturated hydrophobic chains with 6 to 10 carbons.
3) Have almost all unsaturated hydrophobic chains with 16 to 20 carbons.
4) Have almost all unsaturated hydrophobic chains with 6 to 10 carbons.

Correct Answer is: 1


24. What is the most likely reason for a positive afterpotential?

1) electrical capacitance.
2) an increase in sodium conductance during the course of the action potential.
3) an increase in potassium conductance during the course of the action potential.
4) positive afterpotentials are 5-10 mV depolarizations (membrane potential moves towards positive values) which occur as the direct result of transmitter binding to the postsynaptic membrane.
5) an increase in chloride conductance during the course of the action potential.

Correct Answer is: 3


25. At the peak of the action potential, which of the following best describes the order of membrane permeabilities or conductances?

1) sodium (greatest), potassium (less), chloride (least).
2) chloride (greatest), sodium (less), potassium (least).
3) potassium (greatest), sodium (less), chloride (least).
4) sodium (greatest), chloride (less), potassium (least).
5) potassium (greatest), chloride (less), sodium (least).

Correct Answer is: 1


26. Approximately, what is the duration of an action potential?

1) 2 microseconds.
2) 2 milliseconds
3) 0.2 seconds
4) 2 seconds

Correct Answer is: 2


27. What is the intermediate when during fermentation, pyruvate is broken down to form ethanol?

1) Malate.
2) Lactate.
3) PEP.
4) Acetaldehyde.
5) None - Pyruvate is isomerized to form Ethanol.

Correct Answer is: 4


28. True or False: With respect to movement across a cell membrane, facilitated diffusion of a single type of molecule, as an isolated process considered separately from other processes, requires energy in order to "facilitate" movement of some solute across a membrane.

1) True.
2) False.

Correct Answer is: 2


29. Typically, what is the approximate value of the potassium Nernst potential at 37 degrees?

1) -62 microVolts
2) +62 microVolts
3) -62 milliVolts
4) +62 milliVolts
5) zero

Correct Answer is: 3


30. Where would you find a lipoamide side chain?

1) in the reactions of glycolysis
2) as part of the malate-aspartate shuttle.
3) in the reactions of lactic acid fermentation.
4) in the reactions of the pyruvate dehydrogenase complex.

Correct Answer is: 4


31. Which of following best describes the use of beta-oxidation in metabolism?

1) breaks phosphate-phosphate bonds in nucleoside triphosphates.
2) breaks off methyl groups from fats.
3) breaks off carboxyl groups from fats.
4) oxidizes a sulfhydryl group or groups in the pyruvate dehydrogenase complex
5) breaks off two carbon fragments from fatty acids.

Correct Answer is: 5


32. When sailing ships began world exploration, the crew often contracted a disease called beriberi, the symptoms of which can include weakness, fatigue, and nerve damage. We now know that beriberi is caused by a deficiency in thiamine, which is also called vitamin B1. Where is thiamine needed in the human body?

1) in the reactions of glycolysis
2) as part of the malate-aspartate shuttle.
3) in the reactions of lactic acid fermentation.
4) in the reactions of the pyruvate dehydrogenase complex.

Correct Answer is: 4


33. What is the intermediate when during gluconeogenesis, pyruvate is converted to form phosphoenolpyruvate?

1) Lactate.
2) Acetaldehyde.
3) Malate.
4) Glutamate.
5) Oxaloacetate.

Correct Answer is: 5


34. In prokaryotes, the production of ethyl alcohol occurs as the result of:

1) fermentation.
2) the electron transfer chain.
3) the pyruvate dehydrogenase complex in the mitochondria.
4) the citric acid cycle.

Correct Answer is: 1


35. The relatively high Gibbs energy required to add a phosphate to ADP to form ATP is partly the result of:

1) the lower entropy of ATP as compared to the sum of the entropies of ADP and phosphate.
2) the allosteric characteristics of ATP.
3) the electrostatic attraction of the phosphate groups.
4) hydrophobic interactions between phosphate and water.

Correct Answer is: 1


36. True or False: Bacterial aldolases use a mechanism in which the enzyme covalently binds to the substrate via a sulfhydryl group?

1) True
2) False

Correct Answer is: 2


37. Yes or No: Does fermentation ever occur in any type of living human cell?

1) Yes
2) No

Correct Answer is: 1


38. Suppose that we discover a new type of cell. It is shown that only one ion, with charge -2, can freely diffuse across this cell's membrane. The concentration of this ion is 10 mM inside the cell and 1 mM outside the cell. What can we say about the membrane potential?

1) The inside of the cell must be have a negative membrane potential with respect to the outside of the cell.
2) The inside of the cell must be have a positive membrane potential with respect to the outside of the cell.
3) The membrane potential is zero.

Correct Answer is: 2


39. While doing some research on a newly discovered marine invertebrate, you find that its cells are only permeable to one type of ion. But you do not know what ion it is. You determine that the concentration of this ion outside the cells is 10 mM and the concentration inside the cells is 0.1 mM. The membrane potential is -62 mV at 37 degrees C. Which of the following is most likely the ion in question?

1) Iron (+3)
2) Potassium (+1)
3) Calcium (+2)
4) Phosphate (-2)
5) Chloride (-1)

Correct Answer is: 4


40. Which of the following provides the energy to add glucose-1-phosphate units to a growing glycogen chain?

1) NAD+
2) GTP
3) UTP
4) CTP

Correct Answer is: 3