Biology 2107/03



Biology 2107/03 Name               

Fall 2000 Be sure to put your name

Second Examination on the mark-sense sheet as well

Version A

Directions:

• Be sure to put your name on the mark-sense sheet and on the exam booklet. Both must be turned in at the end of the period.

• Indicate the correct version letter of your exam in the upper right corner of the mark-sense sheet in the box marked “KEY ID.”

• Each questions has only one correct answer. When a group of choices is used for more that one question, a choice may be used more than once.

• You may write in the exam booklet, but only the mark-sense sheet will be graded. No other paper, scratch paper, etc., may be used.

• Students must turn in the exam before leaving the room for any reason. A student may not continue working on the exam after having left the room.

Multiple Choice. 50 questions, 2 pt each.

The following choices are used for questions 1 – 4.

(a) Microfilaments

(b) Microtubules

(c) Intermediate filaments

1. These are composed of actin.

2. These play a major role in maintaining the shape of cells. They also mediate changes in cell shape, such as in the pseudopods of an amoeba or the stress fiber attachments of a cell in culture.

3. These play a major role in the movement of organelles and other large particles within a cell.

4. Of the three types of cytoskeletal fibers, this is the only one that is NOT characterized by the possibility of rapid assembly and disassembly.

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The following diagram shows the structure of phosphatidyl ethanolamine and applies to questions 5 - 10.

[pic]

5. Which of the following best describes the overall structure that is shown?

(a) Triglyceride (d) Phospholipid

(b) Amino Acid (e) Disaccharide

(c) Cholesterol

6. Which of the following terms best describes the part labeled “A” in the diagram?

(a) Fatty acid chain (d) Monosaccharide

(b) Amino Acid (e) Active site

(c) Polar head group

7. Which of the following terms best describes the part labeled “B” in the diagram?

(a) Fatty acid chain (d) Monosaccharide

(b) Amino Acid (e) Active site

(c) Polar head group

8. Which of the following terms best describes the solubility of this substance (overall structure) in water?

(a) hydrophobic (d) dualistic

(b) hydrophilic (e) multiphasic

(c) amphipathic

9. This substance is sold in powdered form by chemical supply houses. If some of the powdered form of this substance were mixed thoroughly with water, what would happen?

(a) The substance would separate from the water and float to the top.

(b) The substance would completely dissolve in the water, making a uniform solution.

(c) The substance would become chemically oxidized.

(d) The substance would become chemically reduced.

(e) The substance would form microscopic spherical vesicles, suspended in the water, with the surface of the vesicles made up of lipid bilayers.

10. If you wanted to isolate this substance from a cell, where should you look?

(a) In the plasma membrane

(b) In the cytoplasm

(c) In the matrix of the mitochondrion

(d) In the chromatin of the nucleus.

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11. Some integral membrane proteins have the ability to move. How would you best characterize this membrane protein mobility?

(a) The proteins have free movement in all directions within, across, and through the membrane (the “free-wheeling” model).

(b) The proteins can move transversely (“flip-flop”) from one side of the membrane to the other, but they cannot move laterally (side-to-side) (the “trans-crystalline” model).

(c) The proteins can move laterally (side-to-side), but they cannot transversely (“flip-flop”) from one side of the membrane to the other (the “fluid mosaic” model).

(d) The proteins completely move out of the phospholipid bilayer and travel through the inside of the cell (through the cytoplasm) until they reach the phospholipid bilayer on the other side (the “subway shuttle” model).

(e) The proteins completely move out of the phospholipid bilayer and travel around the outside of the cell (through the aqueous fluid in which the cell is suspended) until they reach the phospholipid bilayer on the other side (the “perimeter bypass” model).

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The following choices are used for questions 12 - 15.

(a) Simple diffusion directly across a phospholipid bilayer

(b) Facilitated diffusion across a membrane

(c) Active transport across a membrane

(d) Both (a) and (b)

(e) Both (b) and (c)

12. Small hydrophobic and polar molecules (such as O2, CO2, N2, H2O, and glycerol) can pass through a membrane by this mechanism, but larger uncharged polar molecules and ions (such as glucose, Na+, and K+) cannot pass through a membrane by this mechanism.

13. This process is almost always mediated by a membrane-bound carrier protein.

14. This process requires the expenditure of the cell’s energy, usually in the form of ATP hydrolysis or energy stored in a concentration gradient.

15. In this process, the substance being transported moves from a high concentration to a low concentration until equilibrium is reached.

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16. A symport

(a) is a channel protein.

(b) is a carrier protein that transports only a single type of solute.

(c) is a carrier protein that transports two different solutes, each from the same side of the membrane.

(d) is a carrier protein that transports two different solutes, one from one side of the membrane and one from the other side of the membrane.

(e) is a synthetic carrier of ions (also known as an ionophore) useful as a model for ion transport studies.

17. What is the function of the Na+-K+ ATPase pump in the plasma membrane of cells?

(a) For each cycle in its mechanism, it transports three sodium ions (Na+) into the cell, two potassium ions (K+) out of the cell, and hydrolyzes one ATP molecule.

(b) For each cycle in its mechanism, it transports three sodium ions (Na+) out of the cell, two potassium ions (K+) into of the cell, and hydrolyzes one ATP molecule.

(c) For each cycle in its mechanism, it transports three sodium ions (Na+) into the cell, two potassium ions (K+) out of the cell, and synthesizes one ATP molecule.

(d) For each cycle in its mechanism, it transports three sodium ions (Na+) out of the cell, two potassium ions (K+) into the cell, and synthesizes one ATP molecule.

18. The protein that coats endocytotic vesicles and secretory vesicles is called

(a) actin (d) clathrin

(b) tubulin (e) laughin

(c) porin

19. Read the following statements about enzyme action:

I. Enzymes are catalysts.

II. Enzymes significantly change the free energy ((G) of a reaction by changing the final equilibrium concentrations of the reactants and products.

III. Enzymes lower the activation energy of a reaction by creating a stabilized intermediate state known as an “Enzyme-Substrate Complex”

IV. Amino acid side chains in the enzyme do not interact with the substrate, because the enzyme molecule must be unchanged at the end of the reaction.

V. The cell must manufacture a new enzyme molecule for each substrate molecule that it converts to product (the law of enzyme-substrate stoichiometry).

Which of the following is correct?

(a) Only statement I is true.

(b) Only statements I, III, and V are true.

(c) Only statements I and III are true.

(d) Only statements I, II, and III are true.

(e) Only statements I, IV, and V are true.

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The following choices are used for questions 20 – 25.

(a) cohabitant (d) competitive inhibitor

(b) cofactor (e) noncompetitive inhibitor

(c) coenzyme

20. This is a substance that is chemically similar to the substrate of an enzyme and can bind to the enzyme’s active site, blocking access by the substrate.

21. This is a substance that is not part of the amino acid structure of an enzyme, but is required for the activity of certain enzymes. This term specifically refers to a substance that is noncovalently bound to the enzyme.

22. This is a substance that is not part of the amino acid structure of an enzyme, but is required for the activity of certain enzymes. This term specifically refers to a substance that is covalently bound to the enzyme.

23. NAD is an example of this.

24. Suppose I am studying an enzyme-catalyzed reaction. When I added a certain substance “XYZ” to the enzyme-substrate mixture, the reaction stopped. However, when I added more substrate, the reaction started back again. What type of substance is substance “XYZ”?

25. High concentrations of ATP in a cell stop the action of phosphofructokinase, one of the early enzymes in the glycolytic pathway. Structural studies have shown that the ATP does not bind to the active site of the enzyme; instead, it binds to a different location and changes the conformation of the enzyme. Which of the terms given above best describes what ATP does to phosphofructokinase?

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The following choices are used for questions 26 – 31.

(a) oxidation

(b) reduction

26. During glycolysis, NAD is converted into NADH. What has happened to the NAD?

27. A process in which an atom gains electrons.

28. This process can occur when an atom becomes bonded to another atom than is less electronegative.

29. In biological systems, this process often occurs when an atom becomes bonded to hydrogen.

30. Imagine a chemical reaction in which carbon dioxide is converted into methane (CH4). What has happened to the carbon atom in this reaction?

31. During fermentation in human muscle tissue, pyruvic acid is converted into lactic acid. What has happened to the pyruvic acid in this process?

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The following choices are used for questions 32 – 34.

(a) catabolism

(b) anabolism

32. This term refers to the processes by which a living organism obtains its energy and raw materials from nutrients.

33. Glycolysis and respiration are examples of this type of process.

34. A synonym for this term is “biosynthesis.”

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The following choices are used for questions 35 - 45.

(a) glycolysis

(b) fermentation

(c) respiration

35. The final electron acceptor in this process is oxygen (in almost all organisms)

36. The final electron acceptor in this process is an acid or alcohol derived from pyruvic acid.

37. In the first stage of this process, two ATP are used up (and converted to ADP).

38. The net yield of ATP in this process is two ATP per molecule of glucose.

39. During this process, the carbons of pyruvic acid are completely oxidized to form three CO2 molecules.

40. Of the tree processes listed, this one is responsible for synthesis of the greatest number of ATP.

41. When fatty acids are converted into acetyl CoA, their carbons are metabolized by this process.

42. In this process, electrons are transferred from NADH to pyruvic acid.

43. In this process, electrons are transferred from NADH to a series of electron carriers in the inner mitochondrial membrane.

44. In this process, electrons are transferred from a three-carbon intermediate (derived from glucose) to NAD.

45. A synonym for this pathway is the Embden-Meyerhoff-Parnas pathway.

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46. During respiration, which of the following processes is most directly responsible for the synthesis of the greatest amount of ATP?

(a) the conversion of glucose into pyruvic acid

(b) the conversion of pyruvic acid into lactic acid

(c) the conversion of pyruvic acid into acetyl CoA and CO2

(d) the citric acid (Kreb’s) cycle

(e) the respiratory electron transport chain

47. The major purpose of fermentation in bacteria and yeast is

(a) the synthesis of organic acids to regulate the pH of the organism’s environment.

(b) to provide a means for bacteria to identify each other by the production of different fermentation end products.

(c) to produce large quantities of ATP from pyruvic acid, since very little ATP is produced during glycolysis.

(d) to oxidize NADH into NAD.

(e) to regenerate ADP for the process of glycolysis.

48. Adenosine triphosphate (ATP) is a good “common currency” of energy for the cell because

(a) it is highly unstable, breaking down rapidly to provide the cell with a “boost” of energy.

(b) its (G of hydrolysis is about –7.5 kcal/mol, making ATP hydrolysis a thermodynamically favorable reaction.

(c) the phosphate group that is released during ATP hydrolysis may become attached to a protein, causing the protein to undergo a conformational change and to do useful work.

(d) Both (a) and (b) are true.

(e) Both (b) and (c) are true.

49. Which of the following can affect the fluidity of a membrane?

(a) The size of the polar head groups in its phospholipids.

(b) The number of carbon-carbon double bonds in the fatty acid chains of its phospholipids.

(c) The presence of cholesterol.

(d) More than one of the above.

(e) None of the above.

50. The best term to describe the diffusion of water molecules across a semipermeable membrane is called

(a) pinocytosis

(b) phagocytosis

(c) osmosis

(d) halitosis

(e) active transport

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