Quiz 4, BICH 410 (TuTh 12:45-2), Thursday, Dec. 5, 1996

Clearly circle the letter corresponding to your answer for each problem. There are seven problems, six of which count 3 points, and one is worth 2 points, and one bonus question for 2 points. No partial credit given for multiple-choice questions.

gas constant R 8.315 J/mol-K; Faraday constant F 96.5 kJ/mol-volt

1. In the biological degradation pathway of glucose, the enzyme pyruvate kinase catalyzes this reaction:
phosphoenolpyruvate + ADP <-> pyruvate + ATP

Given the information below, calculate the standard free energy change for the above reaction.
ATP <-> ADP + Pi; G°' = -30.5 kJ/mol
phosphoenolpyruvate <-> pyruvate + Pi; G°' = -61.9 kJ/mol
glucose + Pi <-> glucose-6-phosphate; G°' = +13.8 kJ/mol

Answer: C

2. Which of the following statements is NOT true about the sodium-potassium ATPase?

Answer: C

3. An integral membrane protein will commonly be solubilized by extraction with:

Answer: B

4. Which of the following types of membrane transport systems is NOT saturable with the molecule or ion that is being transported?

Answer: A

5. Consider the transport of K+ from the blood, where its concentration is about 4 mM, into an erythrocyte that contains 150 mM K+. The transmembrane potential is about 60 millivolts, inside negative relative to outside. The free energy change for this transport process is (assume 37°C):

Answer: Actually, none of these answers is correct, because I blew it. If the question stated "inside positive relative to the outside", as I thought, then:
Gt = RT ln(C2/C1) + ZF(membrane potential)
Gt = (8.315 J/mol-K)(310 K)/(1000 J/kJ) ln 150/4 + (1)(96.5 kJ/mol-V)(.06 V)
Gt = 9.34 + 5.79 = 15.1 kJ/mol

6. (2 pts) A common secondary structure for a transmembrane protein is:

Answer: B

7. When a bacterium such as E. coli is shifted from a warmer growth temperature to a cooler growth temperature, it compensates by:

Answer: D