CITRIC ACID CYCLE. 1. Assume you have a solution containing the pyruvate dehydro
ID: 45704 • Letter: C
Question
CITRIC ACID CYCLE.
1. Assume you have a solution containing the pyruvate dehydrogenase complex and all the enzymes of the TCA cycle, but none of the metabolic intermediates. When you supplement this solution with 5 nmoles each of pyruvate, oxaloacetate, coenzyme A, NAD+, FAD, GDP, AND Pi you find that 5nmoles of CO2 are evolved and then the reaction stops. When you add alcohol dehydrogenase and its substrate acetaldehyde, additional CO2 is produced.
a)How do you explain this result?
b) How many nmoles of acetaldehyde are required to allow complete oxidation of the pyruvate to 15 nmoles of CO2?
Explanation / Answer
a) Acetaldehyde is converted to ethanol with the reaction catalyzed by alcohol dehydrogenase. This reaction produces NAD+. The produce NAD+ is used to carryout pyruvate dehydrogenase reaction, where additional CO2 is produced when pyruvate is converted to acetyl CoA.