Tca Cycle Chemistry Paper printable pdf download

Tca Cycle Chemistry Paper

PROBLEM SET 3

TCA cycle

To date this quarter you have encountered reactions involving the cofactors listed below:

biotin

lipoic acid

thiamin pyrophosphate

flavin adenine dinucleotide (FAD)

co-enzyme A

NAD

Indicate the type of reaction that each cofactor is typically involved in.

Suggest a likely or possible enzyme catalyzed reaction sequence whereby α−ketoadipic

acid (an α-keto, six carbon dicarboxylic acid) may be synthesized from acetyl CoA and

α−ketoglutarate. Use structures and show all cofactors (they may be abbreviated)

required. Please base your answer on analogous reactions discussed this quarter.

COOH

C=O

(CH 2 ) 3

COOH

3. Malonate inhibits one enzyme of the TCA cycle. If yeast grown aerobically are incubated in

malonate, succinate accumulates. What reaction does malonate inhbit? Write the name of the

enzyme or write the reaction.

4. Suppose you had a patient with a much-elevated level of pyruvate in blood and urine. One

possible explanation is a genetic defect in the enzyme pyruvate dehydrogenase; but another

plausible explanation is a specific vitamin deficiency. Explain first what vitamin might be

deficient in the diet, and why that would account for high urinary excretion of pyruvate. How

would you determine which explanation is correct?

5. In a few words, what is the relationship of the pyruvate dehydrogenase complex reaction to

glycolysis and the citric acid cycle?

6. Briefly describe the possible metabolic fates of pyruvate produced by glycolysis in humans

and explain the circumstances that favor each.

- -

Tca Cycle Chemistry Paper