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The Citric Acid Cycle

Problems

Before the Citric Acid Cycle

The Reactions of the Citric Acid Cycle

Problem : What is the name of the starting material of the citric acid cycle?

Acetyl-coenzyme A.

Problem : What is the term used to describe a process that is both catabolic and anabolic?

Amphibolic.

Problem : Why is the enzyme that catalyzes the conversion of pyruvate to acetyl-CoA called the pyruvate dehydrogenase multienzyme complex?

The enzyme is given this name because it is really a group of three enzymes that work together to perform the reaction. Pyruvate dehydrogenase, dihydrolipoyl transacetylase, and dihydrolipoyl dehydrogenase are the three enzymes that make up the pyruvate dehydrogenase multienzyme complex.

Problem : The enzyme pyruvate dehydrogenase performs a similar function to what glycolytic enzyme? What type of reaction do these two enzymes catalyze?

Pyruvate decarboxylase, an enzyme involved in anaerobic alcoholic fermentation, catalyzes the removal of a carbon dioxide group similar to the function of pyruvate dehydrogenase.

Problem : What is the role of NAD in the conversion of pyruvate to acetyl-CoA?

NAD is responsible for re-oxidizing the lipoamide molecule that is used in the second step of the reaction. In the reaction, NAD is converted to NADH.

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