Citric Acid Cycle

Question 1

Give a brief overview of what happens in the cycle

Answer 1

Electrons are removed from food molecules and are passed on to form NADH and FADH2

Question 2

How is acetyl CoA formed?

Answer 2

Decarboxylation, oxidation and CoA transfer of/to pyruvate in the mitochondrial matrix by pyruvate dehydrogenase

Question 3

What is the function of the GTP produced in the Citric Acid Cycle?

Answer 3

Can be converted to ATP if needed in the body

Question 4

Name three enzymes of the Citric Acid Cycle whose inhibition allows the cycle to be regulated?

Answer 4

Pyruvate dehydrogenase
Isocitrate dehydrogenase
Alpha-ketoglutarate dehydrogenase

Question 5

What inhibits/stimulates pyruvate dehydrogenase?

Answer 5

Inhibition - product build-up by negative feedback
Activation - precursor build-up
not on/off but constant alteration

Question 6

What inhibits/stimulates isocitrate dehydrogenase?

Answer 6

Inhibition - by ATP/NADH

Activation - by ADP

Question 7

What regulatory effect does isocitrate dehydrogenase inhibition have on the Citric Acid Cycle?

Answer 7

• causes a build-up of citrate

- citrate enters the cytoplasm, causing phosphofructokinase to stop glycolysis

Question 8

What inhibits alpha-ketoglutarate dehydrogenase?

Answer 8

ATP/NADH/succinyl CoA

Question 9

What regulatory effect does alpha-ketoglutarate dehydrogenase inhibition have on the Citric Acid Cycle?

Answer 9

• causes a build-up of alpha-ketoglutarate

- use is switched to amino acid production

Question 10

What does amphibolic mean?

Answer 10

Having both anabolic and catabolic functions