Quiz 4, BICH 410 (MWF3-3:50), Friday, Nov. 6, 1998
Clearly circle the letter corresponding to your answer for each problem. There are six problems, four of which count 3 points, and two for 4 points. No partial credit given for multiple-choice questions.
gas constant R 8.315 J/mole-KĄ; Faraday constant F 96.5 kJ/mole-volt
1. Which of the following is true about an enzymatic reaction that proceeds via a "ping-pong" mechanism?
- A) Each substrate molecule can bind to the enzyme independently.
- B) A substrate must bind and be released as product before the second substrate can bind to the enzyme.
- C) The enzyme is inhibited by noncompetitive kinetics.
- D) Two substrate molecules bind simultaneously to an enzyme in an ordered pathway.
- E) The enzyme is inactivated by a suicide inhibitor.
2. (4 pts) A competitive inhibitor is characterized by the following properties:
- A) decreases both Vmax and KM
- B) increases KM with no effect on Vmax
- C) decreases KM with no effect on Vmax
- D) increases Vmax without affecting KM
- E) decreases Vmax without affecting KM
3. Which of the following is NOT involved in the signal transduction pathway that results from binding of the hormone glucagon to its receptor?
- A) A G protein binds GTP.
- B) Cyclic AMP activates protein kinase A.
- C) Adenylate cyclase catalyzes the synthesis of cyclic GMP.
- D) Adenylate cyclase is activated.
- E) An enzyme is activated by phosphorylation.
4. Which of the following statements about allosteric control of enzymatic activity is FALSE?
- A) Allosteric proteins are generally composed of several subunits.
- B) Heterotropic allosteric effectors compete with substrate for binding sites.
- C) Binding of the effector changes the conformation of the enzyme molecule.
- D) An effector may either inhibit or activate an enzyme.
- E) Allosteric enzymes show cooperative substrate binding.
5. The steps of glycolysis between glucose and fructose-1,6-bisphosphate involve all the following except:
- A) an enediol intermediate
- B) phosphofructokinase
- C) ATP-dependent phosphorylation
- D) oxidation by NAD+
- E) phosphoglucoisomerase
6. (4 pts) Which step in glycolysis is inhibited by addition of iodoacetate?
- A) Reaction catalyzed by hexokinase
- B) Conversion of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate
- C) Reaction catalyzed by aldolase
- D) Conversion of dihydroxyacetone phosphate to glyceraldehyde-3-phosphate
- E) Conversion of glucose-6-phosphate to fructose-6-phosphate