Molec Cell Chp. 3

17. Glycolysis yields a net gain of _______ ATP molecules per molecule of glucose. a. 2 b. 4 c. 32 d. 38

a. 2

6. What are the energetic consequences of coupling a reaction with a +ΔG to one with a larger -ΔG? a. An ΔG that is favorable overall and drives the reaction with a +ΔG in the forward direction b. An outcome in which both reactions are energetically unfavorable overall c. An outcome in which the overall ΔG is + d. An outcome in which the overall ΔG is unfavorable

a. An ΔG that is favorable overall and drives the reaction with a +ΔG in the forward direction

4. Which of the following is not true of coenzymes? a. Chemically, they are branched amino acids. b. They serve as carriers of several types of chemical groups. c. They transfer specific chemical groups among a wide range of substrates. d. They work together with enzymes to enhance chemical reactions without being irreversibly altered.

a. Chemically, they are branched amino acids.

The trypsin substrate binding site contains an aspartate residue, which is able to form an ionic bond with which amino acids in its polypeptide substrates? a. Lysine or arginine b. Glutamate or glutamine c. Leucine or phenylalanine d. Serine or threonine

a. Lysine or arginine

17. In polysaccharide biosynthesis, the activated metabolic intermediate of glucose is a. UDP-glucose. b. ADP-glucose. c. TDP-glucose. d. NADP-glucose.

a. UDP-glucose.

45. Nitrogen fixation can be carried out by a. a few species of bacteria. b. bacteria, fungi, and plants. c. all eukaryotes. d. all organisms.

a. a few species of bacteria.

18. All organisms can utilize _______ as a nitrogen source. a. ammonia b. atmospheric nitrogen c. nitrate d. nitrite

a. ammonia

21. In eukaryotic cells, glycolysis takes place in the a. cytosol. b. nucleus. c. mitochondria. d. endoplasmic reticulum.

a. cytosol.

44. Gluconeogenesis can produce glucose, starting with a. lactate. b. pyruvate. c. fatty acids. d. All of the above

a. lactate.

Many coenzymes are vitamins because vitamins are a. necessary components in the human diet. b. present in plants but not in animals. c. absent in gut bacteria. d. present in gut bacteria.

a. necessary components in the human diet.

26. Fatty acids are broken down in a stepwise process, _______ carbons at a time. a. two b. four c. six d. eight

a. two

47. For humans, _______ essential amino acids must be provided by the diet. a. 0 b. 8 c. 18 d. 20

b. 8

12. Which of the following is a key molecule in the electron transport chain in mitochondria? a. Citrate b. Cytochrome c c. Pyruvate d. Tetrahydrofolate

b. Cytochrome c

27. In the light reactions of photosynthesis, a. sugars are synthesized from CO2 and water. b. H2O is converted to O2 and NAD is reduced to NADPH. c. oxidative phosphorylation produces ATP. d. All of the above

b. H2O is converted to O2 and NAD is reduced to NADPH.

Which statement below best describes the usual relationship of the inhibitor molecule to the allosteric enzyme in feedback inhibition of enzyme activity? a. The inhibitor is the substrate of the enzyme. b. The inhibitor is the product of the enzyme-catalyzed reaction. c. The inhibitor is the final product of the metabolic pathway. d. The inhibitor is a metabolically unrelated signal molecule

b. The inhibitor is the product of the enzyme-catalyzed reaction.

11. How many carbons does the acetate group of acetyl CoA have? a. One b. Two c. Three d. Four

b. Two

A reaction in which the substrate glucose binds to the enzyme hexokinase and the configuration of both molecules changes is an example of a. a lock-and-key mechanism. b. an induced fit mechanism. c. competitive inhibition. d. allosteric inhibition.

b. an induced fit mechanism.

13. In plants, the molecule that captures energy from sunlight is called a. NADPH. b. chlorophyll. c. chloroplast. d. chromatin.

b. chlorophyll.

20. Glycolysis produces four molecules of ATP from each molecule of fructose-1,6bisphosphate because a. two molecules of ATP are required to convert glucose to fructose-1,6-bisphosphate. b. fructose-1,6-bisphosphate is converted into two molecules of 1,3-bisphosphoglycerate, each of which produces two ATPs in being metabolized to pyruvate. c. fructose-1,6-bisphosphate is converted into four molecules of 1,3-bisphosphoglycerate, each of which produces one ATP when metabolized to pyruvate. d. None of the above

b. fructose-1,6-bisphosphate is converted into two molecules of 1,3-bisphosphoglycerate, each of which produces two ATPs in being metabolized to pyruvate.

15. The Calvin cycle is involved in the synthesis of _______ from _______. a. fructose; carbon dioxide b. glucose; carbon dioxide c. glucose; water d. maltose; malt

b. glucose; carbon dioxide

23. In glycolysis, the key control enzyme that is inhibited by excess ATP is a. hexokinase. b. phosphofructokinase. c. alcohol dehydrogenase. d. All of the above

b. phosphofructokinase.

2. The lock-and-key and induced-fit models are two alternative models that can explain how enzyme and substrates interact. These two models can be distinguished from one another according to changes in a. reaction solution viscosity as substrates and enzymes bind. b. substrate and enzyme shape as binding occurs. c. reaction solution temperature as a result of the endothermic cooling that occurs during substrate binding. d. reaction solution color during enzyme-substrate binding.

b. substrate and enzyme shape as binding occurs.

The ΔG°′ for hydrolysis of ATP to ADP and Pi is _______ kcal/mole. a. greater than +7.3 b. +7.3 c. -7.3 d. -0.5

c. -7.3

7. What is the change in free energy (ΔG) for the hydrolysis of ATP to ADP and P in the cell? a. -12 kcal/mol b. -1.2 kcal/mol c. -7.3 kcal/mol d. -kcal/mol

c. -7.3 kcal/mol

8. What is the total yield of ATP molecules per molecule of glucose from the process of glycolysis? a. 38 b. 4 c. 2 d. 10

c. 2 but could B (4) also be true since they are asking for the total yield, rather than the net yield???

25. As compared on a per gram basis to carbohydrates, fatty acids produce approximately _______ energy through the oxidation process. a. the same b. 50 percent more c. 2.5 times more d. 10 times more

c. 2.5 times more

Proteins can be covalently modified by the addition of phosphate groups to all but which of the following amino acids? a. Serine b. Threonine c. Arginine d. Tyrosine

c. Arginine

3. Why are chymotrypsin, trypsin, elastase, and thrombin all grouped together as members of the serine protease family? a. Because of the presence of a serine residue, each has similar charge and shape properties in their substrate insertion pockets. b. Because of the presence of a serine residue, each can form a heptahedral complex with its substrate. c. Because of the presence of a serine residue, each can form a tetrahedral transition state with its substrate. d. Because of the presence of a serine residue, each can be modified by cell wall biosynthetic degradative enzyme, chitinase.

c. Because of the presence of a serine residue, each can form a tetrahedral transition state with its substrate.

19. Where do the carbon skeletons of amino acids come from? a. The Calvin cycle b. Gluconeogenesis c. Intermediates in glycolysis and the citric acid cycle d. Photosynthesis

c. Intermediates in glycolysis and the citric acid cycle

10. Between glycolysis and the citric acid cycle (also known as the Krebs cycle), there are two molecules of ATP and two molecule of GTP generated directly. Most of the energy derived from the oxidation of glucose comes from the oxidation of _______ . a. FADH2 generated from the citric acid cycle. b. NADH generated from glcolysis. c. NADH generated from the citric acid cycle. d. NADPH generated from the citric acid cycle.

c. NADH generated from the citric acid cycle.

In allosteric regulation, binding of a small, regulatory molecule to an enzyme _______ the enzyme activity. a. inhibits b. stimulates c. either stimulates or inhibits d. neither stimulates nor inhibits

c. either stimulates or inhibits

28. The Calvin cycle can occur a. in the absence of CO2. b. only in the presence of light. c. in the absence of light. d. only in the absence of oxygen.

c. in the absence of light.

22. In eukaryotic cells, the citric acid cycle occurs in the a. cytosol. b. nucleus. c. mitochondria. d. chloroplasts.

c. mitochondria.

5. All of the following are examples of ways that enzyme activity can be regulated except a. binding to an allosteric site. b. feedback inhibition. c. modulation of intracellular sucrose concentrations. d. phosphorylation.

c. modulation of intracellular sucrose concentrations.

48. A nucleotide is a a. base found in nucleic acids. b. purine or pyrimidine base plus a five-carbon sugar. c. purine or pyrimidine base, a five-carbon sugar, and one or more phosphate groups. d. purine or pyrimidine base, a five-carbon sugar, and three phosphate groups.

c. purine or pyrimidine base, a five-carbon sugar, and one or more phosphate groups

Coenzymes are a. additional enzymes in a pathway. b. proteins that form dimeric enzymes. c. small molecules that work with an enzyme to enhance reaction rate. d. small molecules that allosterically regulate enzymes.

c. small molecules that work with an enzyme to enhance reaction rate.

20. In humans, how many amino acids must be taken up in the diet? a. 0 b. 20 c. 19 d. 9

d. 9

16. Gluconeogenesis normally starts from a. amino acids. b. glycerol. c. lactate. d. All of the above

d. All of the above

16. The hydrolysis of ATP to ADP and phosphate allows glucose-6-phosphate to be synthesized from glucose and phosphate because the a. heat produced from ATP hydrolysis drives glucose-6-phosphate synthesis. b. enzymatic coupling of these two reactions allows the energy of ATP hydrolysis to drive the synthesis of glucose-6-phosphate. c. energy of glucose phosphorylation drives ATP splitting. d. All of the above

d. All of the above

The free-energy change of a reaction is determined by the a. intrinsic properties of the reactants and products. b. concentrations of the reactants and products. c. temperature of the reactants and products. d. All of the above

d. All of the above

Like other catalysts, enzymes a. increase the rate of reactions without being consumed in reactions. b. shift the chemical equilibrium from more reactants to more products. c. do not alter the chemical equilibrium between reactants and products. d. Both a and c

d. Both a and c

43. In the synthesis of glycogen, glucose-1-phosphate reacts with a nucleotide triphosphate to form _______-glucose. a. ADP b. GDP c. CDP d. UDP

d. UDP

1. Enzymes act by a. lowering the overall change in free energy of a reaction. b. decreasing the distance reactants must diffuse to find one another. c. increasing the activation energy. d. decreasing the activation energy.

d. decreasing the activation energy.

Enzymes act by a. lowering the overall free energy change of the reaction. b. decreasing the distance reactants must diffuse to find each other. c. increasing the activation energy. d. decreasing the activation energy.

d. decreasing the activation energy.

19. Under anaerobic conditions, the end product of glycolysis is a. ethanol. b. lactate. c. pyruvate. d. ethanol or lactate.

d. ethanol or lactate.

24. Under anaerobic conditions, the NADH produced by glycolysis is recycled by a reaction that produces NAD+ and a. ethanol. b. lactate. c. pyruvate. d. ethanol or lactate.

d. ethanol or lactate.

14. Animal cells can synthesize glucose (gluconeogenesis) from all of the following except a. lactate. b. amino acids. c. glycerol. d. fatty acids.

d. fatty acids.

9. The end products of anaerobic metabolism of glucose may be any of the following except a. acetaldehyde. b. ethanol. c. lactate. d. methanol.

d. methanol.

18. Under aerobic conditions, the end product of glycolysis is a. ethanol. b. lactate. c. phosphoenolpyruvate. d. pyruvate.

d. pyruvate.

Because of the central role that one amino acid plays in the mechanism by which proteins are cleaved by the enzymes trypsin and chymotrypsin, these enzymes are called _______ proteases. a. histidine b. lysine c. arginine d. serine

d. serine