Carbohydrate Metabolism: Citric Acid Cycle

Question 1

What components from glycolysis are used in the citric acid cycle?

Answer 1

2 pyruvate

Question 2

What must happen before citric acid cycle?

Answer 2

Pyruvate must be oxidized to acetyl-coA by pyruvate dehydrogenase.

Pyruvate dehydrogenase forms (and is inhibited by) acetyl-coA and NADH.

Question 3

Where does the citric acid cycle take place?

Answer 3

The mitochondrial matrix

Question 4

What is the main purpose of CAC?

Answer 4

To oxidize acetyl-coA to CO2 and generate high-energy electron carriers (NADH & FADH2) and GTP.

Question 5

What is the cycle (products and enzymes)?

Answer 5

Question 6

What other molecules can be converted to Acetyl-CoA?

Answer 6

Fatty acids, Ketones, and alcohols

Question 7

What steps in the CAC require electron acceptors?

Answer 7

Pyruvate dehydrogenase requires NAD+
Isocitrate dehydrogenase requires NAD+
alpha-ketoglutarate dehydrogenase requires NAD+
Succinate dehydrogenase (Complex II) requires FAD
Malate dehydrogenase requires NAD+

Question 8

What are the control points of the CAC?

Answer 8

Conversion of pyruvate to acetyl-coA by pyruvate dehydrogenase
Reaction between acetyl-coA and oxaloacetate by citrate synthase
Conversion of isocitrate to alpha-ketglutarate by isocitrate dehydrogenase
Conversion of alpha-ketglutarate to succinyl-coA by alpha-ketoglutarate dehydrogenase

Question 9

Where in the cycle are there inhibition points?

Answer 9

Question 10

What is the rate-limiting step of the cycle?

Answer 10

When isocitrate dehydrogenase oxidizes and decarboxylates isocitrate to form alpha-ketoglutarate

Question 11

What are the products from 1 glucose in the citric acid cycle?

Answer 11

6 NADH (10 NADH when including glycolysis products)
2 ATP (4 ATP when including glycolysis products)
2 FADH
4 CO2