BIOCHEMISTRY 3613

Exam 3 - October 23, 2002Row number: Name:

Multiple choice ( 3 points each):

1. An enzyme catalyzes a reaction by lowering the

(a) free energy of the reaction.

(b) entropy of the reaction.

(c) activation energy of the reaction.

(d) enthalpy of the reaction.

2. The Km of an enzymatic reaction is equal to

(a) the concentration of substrate at equilibrium

(b) the concentration of product at equilibrium

(c) the concentration of substrate at one-half maximum velocity (Vmax)

(d) the concentration of enzyme at one-half maximum velocity (Vmax)

3. In a Lineweaver-Burk plot for an enzymatic reaction, which of the following is determined as the point where the straight line intersects the y axis?

(a) -1/Km

(b) + 1/Km

(c) - 1/Vmax

(d) + 1/Vmax

4. In the Lineweaver-Burk plot for an enzymatic reaction, which of the following is determined as the point where the straight line intersects the x axis?

(a) - 1/Km

(b) + 1/Km

(c) - 1/Vmax

(d) + 1/Vmax

5. Which of the following is true for an enzymatic reaction in the presence of a competitive inhibitor of the substrate?

(a) the Km changes and Vmax stays the same

(b) the Km stays the same and Vmax changes

(c) both Km and Vnaax stay the same

(d) both Km and Vmax change

6. Which of the following is true for an enzymatic reaction in the presence of a non-competitive inhibitor of the substrate?

(a) the Km changes and Vmax stays the same

(b) the Km stays the same and Vmax changes

(c) both Km and Vmax stay the same

(d) both Km and Vmax change

7. The term free energy refers to:

(a) the total energy released accompanying a chemical reaction

(b) the degree of randomness or disorder of a system

(c) that component of the total energy that can do work under isothermal conditions

(d) none of the above

8. Which of the following can be attributed to entropy?

(a) specific dynamic action

(b) metabolic heat loss

(c) basal metabolic rate

(d) none of the above

9. Your breakfast cereal contains 7% protein, 1% fat and 86% carbohydrate, what would be the estimated metabolizable energy content of 100 g of this breakfast cereal based on physiological fuel values?

(a) 393 kcal

(b) 381 kcal

(c) 407 kcal

(d) 150 kcal

10. High-energy compounds exhibit:

(a) a large increase in free energy when they undergo hydrolysis

(b) a large increase in internal bond energy after hydrolysis

(c) a large decrease in free energy when they undergo hydrolysis

(d) a decrease in resonance after hydrolysis

11. Consider the reaction A—> B, if the free energy of B is less than the free energy of A, then G will be:

(a) negative and the reaction is said to be exergonic

(b) positive and the reaction is said to be endergonic

(c) negative and the reaction is said to be exothermic

(d) positive and the reaction is said to be endothermic

12. All of the following are high energy compounds EXCEPT

(a) phosphoenolpyruvate

(b) acetyl CoA

(c) glucose 6-phosphate

(d) ATP

13. If the equilibrium constant of a reaction is 1000, then one would expect the G to be

(a) large and positive

(b) zero

(c) large and negative

(d) there is no relationship between these parameters

14. You notice that your friend can eat twice as much food as you and never seem to gain weight. Which of the following may help explain this observation.

(a) you have a lower basal metabolic rate than your friend

(b) you have a higher basal metabolic rate than your friend

(c) this observation probably has nothing to do with basal metabolic rate

15. Which of the following is sufficient for two reactions to be coupled?

(a) the reactions should be known to exist

(b) one should have a negative standard free energy and the other a positive standard free energy

(c) the rate of one reaction should be significantly faster than the other

(d) an intermediate should be common to both reactions

16. Which of the following states of matter would have the highest entropy?

(a) solid

(b) liquid

(c) gas

(d) they are all about the same

17. Consider the following reactions:

A -----> B, G = - 5.70 kJ/mol

B -----> C, G = - 17.11 kJ/mol

The G for the overall reaction of A ----> C is

(a) + 22.81

(b) - 11.41

(c) + 11.41

(d) - 22.81

18. A coupled reaction involving ATP will proceed

(a) only if the net G is negative

(b) only if the net G is positive

(c) only if it occurs at a rapid rate

(d) only if it involves a common or activated intermediate

19. Which class of compounds is the most oxidized?

(a) alkanes

(b) alcohols

(c) aldehydes

(d) acids

20. Biological oxidation-reduction reactions always involve

(a) transfer of hydrogens

(b) transfer of electrons

(c) formation of water

(d) direct participation of oxygen

21. Nicotinic acid is

(a) a cofactor in oxidation reactions

(b) a component of FAD

(c) a coenzyme for certain dehydrogenases

(d) a component of NAD+

22. The transfer of hydrogens can be represented as

(a) 2H

(b) 2H+ + 2e-

(c) H:- + H+

(d) all of the above

23. Which of the following enzymes catalyze an irreversible reaction in glycolysis?

(a) phosphohexose isomerase

(b) phosphofructokinase

(c) phosphoglycerate kinase

(d) phosphoglycerate mutase

24. Which of the following enzymes catalyze an oxidation-reduction reaction in glycolysis?

(a) hexokinase

(b) enolase

(c) glyceraldehyde 3 phosphate dehydrogenase

(d) aldolase

25. Which of the following enzymes catalyze a reaction in glycolysis that results in the synthesis of a mole of ATP?

(a) hexokinase

(b) phosphofructokinase

(c) pyruvate kinase

(d) glyceraldehyde 3 phosphate dehydrogenase

26. Which of the following enzymes catalyze a reaction in glycolysis that converts ATP to ADP as part of the reaction?

(a) phosphohexose esomerase

(b) phosphofructokinase

(c) phosphoglycerate mutase

(d) aldolase

27. Which of the following enzymes catalyze a reaction which results in the synthesis of a high-energy compound?

(a) aldolase

(b) enolase

(c) phosphoglycerate mutase

(d) triose phosphate isomerase

28. The oxidation of 1 mole of glucose by aerobic glycolysis produces:

(a) 2 moles of pyruvate and 6 moles of ATP

(b) 2 moles of pyruvate, 2 moles of NADH and 4 moles of ATP

(c) 2 moles of lactate and 2 moles of ATP

(d) 2 moles of pyruvate, 2 moles of NAD+ and 4 moles of ATP

29. The oxidation of 1 mole of glucose by anaerobic glycolysis produces:

(a) 2 moles of pyruvate and 6 moles of ATP

(b) 2 moles of pyruvate, 2 moles of NADH and 4 moles of ATP

(c) 2 moles of lactate and 2 moles of ATP

(d) 2 moles of pyruvate, 2 moles of NAD+ and 4 moles of ATP

30. What is the net yield (made minus used) of ATP for the conversion of 1 mole of glucose to 2 moles of ethanol?

(a) 2

(b) 4

(c) 6

(d) 8

31. What is the net yield (made minus used) of ATP for the conversion of 1 mole of glucose to 2 moles of lactic acid?

(a) 2

(b) 4

(c) 6

(d) 8

32. How many ATPs are synthesized by substrate level phosphorylation in aerobic glycolysis during the conversion of 1 glucose to 2 pyruvates?

(a) 0

(b) 2

(c) 4

(d) 6

33. Which of the following enzymes couples with lactic acid dehydrogenase to regenerate NAD+ during anaerobic glycolysis?

(a) phosphofructokinase

(b) aldolase

(c) glyceraldehyde 3 phosphate dehydrogenase

(d) none of the above