Sample biochem quiz : LUSENET : NJMed Class of 2003 : One Thread

Here's one of last year's bmb quizzes (answer key is at the end)...enjoy!:

Medical Biochemistry & Molecular Biology "F-98" Quiz #1 08/28/98 ---------------------------------------------------------------------------------------------------------------------- For each of the following multiple choice questions, choose the most appropriate answer. ---------------------------------------------------------------------------------- 1 . The major component of the body is A. protein. B. fat. C.carbohydrate. D.water. E.nucleic acids.

2. The metabolism of fatty acids, carbohydrates and proteins in humans can each yield A. lactic acid. B. pyruvate. C.acetyl coenzyme A. D.glucose. E.leucine.

3. Which of the following pairs of compounds both contain carboxyl groups? A. acetic acid and glycine B. lactic acid and glucose C. glycerol and pyruvic acid D. ethanol and lactic acid E. glycerol and acetic acid

4. Conversion of acetaldehyde to acetic acid is an example of A. esterification B. hydrolysis. C. dehydration D. condensation. E. oxidation.

5. A solution of glutamic acid is titrated from pH 1.0 to 7.0 by the addition of 5 ml of 1 M NaOH. What is the approximate number of millimoles of amino acid in the sample (pKa1=2.19, pKa2=4.25, pKa3=9.67)? A. 1.25 B. 2.5 C. 5.0 D. 10.0 E. 15.0

6. The approximate isoelectric pH for aspartic acid (pKa1 = 2.09, pKa2=3.86, pKa3=9.82) is represented by which of the following values? A. 2.09 B. 2.97 C. 3.86 D. 6.84 E. 9.82

7. Which one of the following amino acids is most likely to be found in the interior of a globular protein ? A. leucine B. serine C. glutamic acid D. aspartic acid E. arginine

8. Which one of the following features of a protein is considered part of its secondary structure? A. subunit interactions B. sequence of amino acids C. alpha helices D.ligand binding properties E.electrophoretic mobility

9. Which of the following techniques is most useful for determining the size of a protein? A. circular dichroism B. gel filtration C. dialysis D. D. isoelectric precipitation E. E. ultraviolet absorption

10. The absorption of light by proteins at a wavelength of 280 nm is due to the content of A. methionine and cysteine. B. glutamic acid and aspartic acid. C. leucine and valine. D. tyrosine and tryptophan. E. serine and threonine.

11. A mutation that results in an increase in the Km (Michaelis constant) of an enzyme has the following effect on the rate of the reaction: A. The Vmax of the enzyme-catalyzed reaction is increased. B. The rate of the reaction at a given subsaturating substrate concentration is increased. C. The Vmax of the enzyme -catalyzed reaction is decreased. D. The rate of the reaction at a given subsaturating substrate concentration is decreased. E. The rate of the reaction at saturating substrate concentration is decreased.

12. The Km of hexokinase for glucose is 30 microM, and the Km of glucokinase is 10 mM. Which one of the following statements regarding hexokinase, glucokinase, or both enzymes is true when the blood glucose concentration is 10 mM (as found in the hepatic portal vein after a meal)? A. Both hexokinase and glucokinase are operating near maximal velocity B. Hexokinase is operating near maximal velocity. -C. Glucokinase is operating near maximal velocity. D. Neither hexokinase nor glucokinase is operating near maximal velocity.

13. The effect of an enzyme on a reaction is to A. increase the energy of activation. B. decrease the energy of activation. C. increase the AG of the reaction. D. decrease the AG of the reaction. F. increase the equilibrium constant.

14. Which of the following is true of competitive enzyme inhibitors? A.Vmax stays the same. B. The apparent Km remains the same. C. Vmax decreases. D. Increasing concentrations of substrate will not overcome the inhibition. E. The inhibitor binds to a site other than the active site.

15. In the presence of a typical noncompetitive inhibitor of the activity of a particular enzyme towards a given substrate A. the enzyme is irreversibly inactivated. B. the maximum velocity will remain unchanged from that in the absence of the inhibitor. C. the interaction of the inhibitor with the substrate is a major factor leading to the inhibition observed. D. sigmoidal kinetics would be expected if there is no change in protein conformation on the binding of either substrate or inhibitor. E. the apparent Michaelis constant (Km) for the substrate will be the same with or without inhibitor present.

16. Considering the following data for an enzyme: Without inhibitor With 5 mM inhibitor Kr= 0.18 mM 0.36 mM Vmax= 20 20

it may be concluded that A) inhibitor binds to the active site. B) inhibitor binds at the allosteric site C. inhibitor does not compete with the substrate at the active site. D. inhibitor produces irreversible inactivation of the enzyme. E. Ki is lower than 5 mM.

Answer key: 1. d 2. c 3. a 4. d 5. b 6. b 7. a 8. c 9. b 10. d 11. d 12. a 13. b 14. a 15. e 16. a

-- Omar Akhtar (, August 29, 1999

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