TCA Cycle

Question 1

All TCA Cycle enzymes are in the mitochondrial matrix except _____ which is located in the inner mitochondrial membrane.

Answer 1

succinate dehydrogenase

Question 2

The condensation of acetyl-CoA and oxaloacetate produces ______ using the enzyme _____

Answer 2

citrate; citrate synthase

Question 3

This enzyme isomerizes citrate to Isocitrate. This enzyme is also inhibited in Fluoroacetate poisoning

Answer 3

aconitase

Question 4

This is the key regulatory enzyme in TCA Cycle. It oxidizes isocitrate to a-ketoglutarate

Answer 4

isocitrate dehydrogenase

Question 5

The five cofactors of the enzyme a-ketoglutarate dehydrogenase which helps in converting a-ketoglutarate to succinyl CoA

Answer 5

TPP, Lipoic acid, CoASH, FAD, NAD

Question 6

Cleaving the high energy thioester bond in this compound produces GTP.

Answer 6

Succinyl CoA (to Succinate); succinyl-CoA synthase

Question 7

After this step in TCA cycle, 6 of the 8 electrons from the carbons of acetyl CoA are captured

Answer 7

Succinate –> Fumarate produces FADH2

Question 8

The oxidation of ____ leads the production of oxaloacetate

Answer 8

malate via malate dehydrogenase

Question 9

Coenzymes used in converting pyruvate to acety CoA

Answer 9

Thiamine pyrophosphate
Lipoic acid
Coenzyme A

FAD
NAD

Question 10

What is the role of your citric acid cycle?

Answer 10

1. Formation of ATP

2. Substrates for gluconeognesis, aminoacid synthesis, and fatty acid synthesis

Question 11

What step of ETC does not happen in the mitochondrial matrix?

Answer 11

succinate dehydrogenase

it happens in the inner mitochondrial membrane

Question 12

What are the products of 1 cycle of TCA?

Answer 12

1. 2CO2
2. 1 GTP
3. 3 NADH
4. 1 FADH2

Question 13

What is the rate limiting step of citric acid cycle

Answer 13

Isocitrate to alpha-ketoglutarate

isocitrate dehydrogenase

Question 14

What are the co-enzymes needed by the alpha ketoglutarate in converting alpha ketoglutarate to succinyl-CoA?

Answer 14

1. Thiamin pyrophosphate
2. Lipoic acid
3. Coenzyme A
4. FAD
5. NAD

Question 15

What inhibits the enzyme aconitase?

Answer 15

Fluoroacetate

Question 16

[Steps of the TCA cycle: what enzyme is used]

2. Citrate to Isocitrate

Answer 16

Aconitase

Inhibited by Flouroacetate

Question 17

[Steps of the TCA cycle: what enzyme is used]

1. Acetyl CoA + Oxaloacetate to Citrate

Answer 17

Citrate Synthase

Question 18

[Steps of the TCA cycle: what enzyme is used]

3. Isocitrate to alpha ketoglutarate

Answer 18

Isocitrate dehydrogenase

Question 19

[Steps of the TCA cycle: what enzyme is used]

4. alpha ketoglutarate to succinyl CoA

Answer 19

alpha ketoglutarate dehydrogenase

Inhbited by: Arsenite and ammonia

Question 20

[Steps of the TCA cycle: what enzyme is used]

5. Succinyl CoA to Succinate

Answer 20

Succinate thiokinase/Succinyl CoA synthetase

Produce GTP

Question 21

[Steps of the TCA cycle: what enzyme is used]

6. Scuccinate to fumarate

Answer 21

Succinate dehydrogenase

Produce: FADH2

Question 22

[Steps of the TCA cycle: what enzyme is used]

7. Fumarate to malate

Answer 22

fumarase or fumarate hydratase

Question 23

[Steps of the TCA cycle: what enzyme is used]

8. Malate to oxaloacetate

Answer 23

malate dehydrogenase

Produces NADH

Question 24

TCA intermediate that delivers acetyl CoA to cytosol for FA synthesis

Answer 24

Citrate

Question 25

TCA intermediate that is used for heme synthesis and activation of ketone bodies in extrahepatic tissues

Answer 25

succinyl CoA

Question 26

TCA intermediate that can be used for gluconeogenesis

Answer 26

malate

Question 27

What reactions replenish TCA intermediates?

Answer 27

anaplerotic reaction

Question 28

What enzyme maintains adequate concentration of oxaloacetate?

Answer 28

pyruvate carboxylase

Question 29

What are other anaplerotic substrates that can be used to replenish TCA intermediates?

Answer 29

1. Glutamine
2. Glutamate
3. Aspartate
4. Propionyl CoA