Citric Acid Cycle

Question 1

Substrate of citric acid cycle

Answer 1

Acetyl coA

Question 2

How many ATP equivalents is the citric acid cycle?

Answer 2

10 ATP

Question 3

Outline the link raction

Answer 3

1. Glycolysis occurs in cytosol -> pyruvate
2. Pyruvate dehydrogenase converts pyruvate to acetyl coA
3. irreversible

Question 4

Mechanism behind link reaction

Answer 4

1/ Pyruvate oxiised + coASH -> acetyl coA

2. Co2 released
3. NAD -> NADH

Question 5

Which elements of the link reaction are exothermic?

Answer 5

Pyruvate -> acetyl coA and CO2 release

Question 6

Which enzyme is not in the mitochondrial matrix?

Answer 6

Succinate dehydrogenase is in mitochondrial membrane

Question 7

Which 3 enzymes regulate the citric acid cycle?

Answer 7

Citric synthase, Isocitrate dehydrogenase and isogluaterate dehydrogenase

Question 8

Products of citric acid cycle at each stage

Answer 8

1. Oxoloacetate + acetyl coA -> citrate
2. Isocitrate
3. a-ketogluterate
4. Succinyl
5. Succinate
6. Fumarate
7. Malate -> Oxoloacetate

Question 9

Enzymes at each stage

Answer 9

1. Citrate synthase
2. Aconitase
3. Isocirate dehydrogenase
4. a-ketoglutamate dehydrogenase
5. succinyl coA synthetase
6. succinate dehydrogenase
7. fumerase
8. Malate dehydrogenase

Question 10

At which stages are NADH and CO2 released?

Answer 10

1. When Isocitrate is converted to a-ketogluterate by isocitrate dehydrogenase
2. When alphaketogluterate is converted into succinyl by a-ketogluterate dehydrogenase
3. Conversion of malate to oxoloacetate produces NADH

Question 11

At which stage is coA released?

Answer 11

When a-ketoglutamate is converted into succinyl by a-ketoglutamate dehydrogenase

Question 12

At which stages are FADH2 produced?

Answer 12

When succcinate is converted to fumerate by succinly coA synthetase

Question 13

At which stage is GTP produced?

Answer 13

When succinyl is converted succinate by succinyl coA synthetase

Question 14

At which stage is H2O produced?

Answer 14

When fumerate is converted to malate by fumerase

Question 15

Regulation of ciric acid cycle

Answer 15

Occurs in all mitochondria because ATP requirement changes

Question 16

How would the body increase the activity of the citric acid cycle?

Answer 16

1. Increase activity of regulatory enzymes
2. Increase supply of acetyl coA
3. Increase conc. of intermediates

Question 17

In the fed state

Answer 17

Glycolysis -> acetyl coA

Question 18

In the fasting state:

Answer 18

Acetyl coA from FA b/c glycolysis inhibited

Question 19

During ezercise:

Answer 19

CAC enzymes stimulated, acetylcoA supply increases and conc. of intermediates increases