BIOCHEMISTRY 4613/6613
Exam 1 - January 29, 1999
Row number: Name:
Multiple choice ( 3 points each):
1. If the free energy of a reaction in a particular direction is negative
(a) the reaction will not proceed spontaneously
(b) the reaction will proceed spontaneously
(c) the reaction is not reversible
(d) there is no overall increase in entropy
(e) there is a large decrease in entropy
2. Standard free energy is
(a) the difference in gravitational fields between two molecules.
(b) the expression of maximum useful energy change in a system
(c) always a positive value in spontaneous reactions
(d) closely related to the Vmax of an enzymatic reaction
(e) none of the above
3. 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
(e) a reduction in reducing potential after hydrolysis
4. Standard free energy of a reaction can be used for all of the following EXCEPT
(a) predict the direction in which a reaction will proceed under standard conditions of temperature, concentrations and pH.
(b) predict free energy changes for reactions given the concentrations of reactants and products that are unequal to 1 M.
(c) predict the rate of a chemical reaction.
(d) predict the standard free energy change of the reaction at pH 7.
(e) predict the equilibrium constant for a reaction.
5. Your doctor suspects that you have a hyperthyroid condition and arranges for you to take a BMR. Why would he do this?
(a) BMR is normally elevated in hyperthyroid patients.
(b) BMR is normally decreased in hyperthyroid patients.
(c) your doctor doesn't have any idea what is wrong with you.
6. If your breakfast cereal contains 22 grams of carbohydrate, 1 gram of fat and 2 grams of protein per serving, how many kcal would you estimate your cereal to have per serving?
(a) 55
(b) 105
(c) 145
(d) 205
(e) 255
7. In the reactions, A -> B, B ->C, and C -> D, the standard free energy changes are -5, +6 and -9 kcal, respectively. The standard free energy change for A -> D would be
(a) +6
(b) -8
(c) -9
(d) -14
(e) -20
8. The conversion of glucose 6-phosphate to fructose 6-phosphate has a standard free energy change of +1.7 kJ/mole. The equilibrium constant for the reaction
(a) cannot be determined from the data given.
(b) is less than one.
(c) is greater than one.
(d) changes with the concentration of enzyme.
(e) depends on the concentration of glucose 6-phosphate.
9. In general, coupling of two biosynthesis reactions involve:
(a) two endergonic reactions, one of which has a larger standard free energy than the other.
(b) one exergonic reaction with a standard free energy smaller than an associated endergonic reaction.
(c) two endergonic reactions, one having a lower standard free energy than the other.
(d) one exergonic reaction having a standard free energy larger than the standard free energy of an associated endergonic reaction.
(e) none of the above
10. Which class of compounds is the most reduced?
(a) carboxylic acid
(b) aldehyde
(c) alcohol
(d) alkane
11. The structure of NADH does NOT contain
(a) an adenine nucleotide
(b) phosphate
(c) nicotinic acid
(d) riboflavin
12. What is the net ATP yield for the conversion of one molecule of glucose to 2 moles of ethanol?
(a) 0
(b) 2
(c) 4
(d) 6
(e) 8
13. What is the net ATP yield for the conversion of one molecule of glucose to 2 moles of pyruvate?
(a) 0
(b) 2
(c) 4
(d) 6
(e) 8
14. Which of the following enzymes catalyze a reaction in glycolysis that results in substrate level phosphorylation?
(a) Hexokinase
(b) Phosphofructokinase
(c) Glyceraldehyde 3-phosphate dehydrogenase
(d) Phosphoglycerate kinase
(e) Enolase
15. Which of the following enzymes catalyze a reaction in glycolysis that results in the production of a high energy compound?
(a) Hexokinase
(b) Phosphofructokinase
(c) Glyceraldehyde 3-phosphate dehydrogenase
(d) Aldolase
(e) Phosphoglycerate mutase
16. The standard free energy for the hydrolysis of ATP is about
(a) - 7.3 kJ/mole
(b) -20.5 kJ/mole
(c) -30.5 kJ/mole
(d) -40.5 kJ/mole
17. Which of the following enzymes catalyze the commitment step in glycolysis?
(a) Hexokinase
(b) Phosphofructokinase
(c) Pyruvate kinase
(d) Glucose 6-phosphate dehydrogenase
(e) Phosphoglycerate kinase
18. The oxidation of 1 mole of glucose by the pentose shunt would result in the production of:
(a) 1 mole of pentose, 1 mole of NADH, and 1 mole of carbon dioxide
(b) 1 mole of pentose, 2 moles of NADH, and 1 mole of carbon dioxide
(c) 1 mole of pentose, 1 mole of NADPH, and 1 mole of carbon dioxide.
(d) 1 mole of pentose, 2 moles of NADPH, and 1 mole of carbon dioxide
19. End products of the pentose shunt can reenter glycolysis as:
(a) glucose 6-phosphate
(b) fructose 6-phosphate + glyceraldehyde 3-phosphate
(c) fructose 1,6 bisphosphate
(d) dihydroxyacetonephosphate
(e) all of the above
20. Which of the following enzymes catalyze a reaction that produces carbon dioxide?
(a) Glyceraldehyde 3-phosphate dehydrogenase
(b) Lactic acid dehydrogenase
(c) Alcohol dehydrogenase
(d) Glucose 6-phosphate dehydrogenase
(e) 6-Phosphate Gluconic acid dehydrogenase
21. The pentose shunt is considered to be an important alternate aerobic pathway for glucose oxidation in all the following tissues EXCEPT
(a) liver
(b) muscle
(c) adipose tissue
(d) mammary gland
(e) adrenal cortex
22. Which of the following coenzyme forms has a strong absorbance at 340 nm?
(a) NAD+
(b) NADH
(c) FAD
(d) FADH2
(e) FMN
23. A coupled reaction involving ATP will proceed
(a) only if the net change in free energy is negative
(b) only if the net change in free energy is positive
(c) only if it occurs at a rapid rate
(d) only if it involves a common or activated intermediate
24. Biological oxidation-reduction reactions always involve
(a) transfer of hydrogens
(b) transfer of protons
(c) transfer of electrons
(d) formation of water
(e) direct participation of oxygen
Short answer: USE NAME REACTIONS - NO STRUCTURES REQUIRED
1. In general, the large decrease in free energy which occurs during the hydrolysis of high energy compounds is due to the products being more stable than the reactants. List four factors that contribute to the greater stability of the products and give an example of a high energy compound that illustrates each factor. (8 points)
2. Show by word reactions how pyruvate is converted to ethanol, include the names for the reactants and products, name the enzyme(s) and cofactor(s) involved. (8 points)
3. What is the unique association between the above reaction, i.e. conversion of pyruvate to ethanol, that allows for the anaerobic conversion of glucose to ethanol, an oxidation-reduction process, during alcohol fermentation? Use name reactions as well as names of enzymes and coenzymes if appropriate. (6 points)
4. List three important functions of the pentose shunt. (6 points)