Biochemistry Notes

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BCH 3023 – Fall 2008 Final Exam, 12/8/2008 Name: _________________________________ 1. The GTP analog, ,-imidoguanosine 5’-triphosphate (Gpp(NH)p), shown below, cannot be hydrolyzed between the  and  phosphates. Predict the effect of microinjection of Gpp(NH)p of G-protein coupled signaling. O

N NH

O

O H N P OO

O P OH OH OH O H

N

N

NH2

-

O

P O-

O H H

a. Gpp(NH)p is a substrate for adenylate cyclase and, thus, will decrease the intracellular concentration of cAMP. b. The G-Gpp(NH)p complex will be deactivated, thereby, decreasing the intracellular concentration of cAMP. c. The G-Gpp(NH)p complex will be activated, thereby, increasing the intracellular concentration of cAMP. d. Gpp(NH)p will stabilize the G, complex, thereby, decreasing the intracellular concentration of cAMP. e. Gpp(NH)p will destabilize the G, complex, thereby, increasing the intracellular concentration of cAMP. 2. Gluconeogenesis must use “bypass reactions” to circumvent three reactions that are highly exergonic and essentially irreversible. Reactions carried out by which three of the enzymes listed must be bypassed in the gluconeogenic pathway? 1) 2) 3) 4) 5) Hexokinase Phosphoglycerate kinase Phosphofructokinase-1 Pyruvate kinase Triosephosphate isomerase

a. b. c. d. e.

1, 2, and 3 1, 2, and 4 1, 3, and 4 2, 3, and 4 2, 4, and 5

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BCH 3023 – Fall 2008 Final Exam, 12/8/2008
3. The reaction, A + 2B  C, has an equilibrium constant of 1  106 M-2 and a G° of -34.2 kJ/mol. If the concentrations of A, B, and C are all 1.0 mM and the temperature is 25 °C, a. b. c. d. e. the G for the reaction is negative and the reaction will proceed from left to right. the G for the reaction is positive and the reaction will proceed from right to left. the G for the reaction is zero and the reaction is at equilibrium. the G = G° and lnQ = 0. The G = lnQ and G° = 0.

4. For the reaction A  B, G°' = –60 kJ/mol. The reaction is started with 100 mM A at 37 °C; no B is initially present. After 48 hours, analysis of reveals the presence of 10 mM B and 90 mM. Which of the following is the most likely explanation?

a. b. c. d. e.

This result described is impossible, given that the G°' = –60 kJ/mol. There must be an enzyme that shifts the equilibrium toward A. A and B have reached their equilibrium concentrations. The formation of B is kinetically slow; equilibrium has not been reached in 48 hours. The formation of B is thermodynamically unfavorable.

5. Glucose labeled in the carbon atoms shown in the text box below would yield which labeled pyruvate? a. 14CH3-14CO-14COOH b. 14CH3-14CO-COOH c. 14CH3-CO-COOH d. 14CH3-CO-14COOH e. CH3-14CO-14COOH HO CH2 C C H OH HO 14 C H H

14

O

H
14

C

OH

C

OH

6. During stenuous exercise, the NADH formed in the glyceraldehydes 3-phosphate dehydrogenase reaction in skeletal muscle must be reoxidized to NAD+ if glycolysis is to continue. The most important reaction in skeletal muscle for the reoxidation of NADH is: a. b. c. d. dihydroxyacetone phosphate  glycerol 3-phosphate glucose 6-phosphate  fructose 6-phosphate pyruvate  lactate malate  oxaloacetate e. oxaloacetate  phosphoenolpyruvate 7. Fructose 1-phosphate aldolase catalyzes a reaction that: a. b. c. d. e. yields dihydroxyacetone phosphate and glyceraldehyde 3-phosphate. is important in feeding D-fructose into glycolysis. yields fructose 6-phosphate and inorganic phosphate (P i). interconverts dihydroxyacetone phosphate and glyceraldehyde 3-phosphate. is important in the conversion of pyruvate to lactate.

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BCH 3023 – Fall 2008 Final Exam, 12/8/2008
8. A mutation in PKA has been identified that prevents the binding of cAMP to the R-subunit, but still allows normal interactions between the R- and C-subunits. What is the consequence of this mutation?

a. The insulin receptor protein (INS-R) cannot form the active ()2 dimer. b. Autophosphorylation of the insulin receptor protein...
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