Chapter 10: 10.1 Citric Acid Cycle

Question 1

Define:

PDC

Answer 1

Pyruvate Dehydrogenase Complex
* Links pyruvate production from the cytoplasm to the citric acid cycle in the mitochondrial matrix
* Completes an oxidative decarboxylation reaction

Question 2

What does PDC require?

(6 points)

Answer 2

• Thiamine
• Pyrophosphate
• Lipoamide
• Coenzyme A
• FAD
• NAD+

Question 3

What does PDC produce?

(3 points)

Answer 3

• CO2
• Acetyl CoA
• NADH + H+

Question 4

How many subunits is PDC made up of? What are they?

Answer 4

3
* E1: Pyruvate dehydrogenase
* E2: Dihydrolipoamide acetyltransferase
* E3: Dihydrolipoamide dehydrogenase

Question 5

What are the ways the pyruvate dehydrogenase regulated?

Answer 5

1. Feedback Inhibition
2. Covalent Modification
3. Allosteric Control

Question 6

In Regulation of Pyruvate Dehydrogenase:

How does Feedback Inhibition regulate pyruvate dehydrogenase?

Answer 6

Inhibited by products of Acetyl-CoA and NADH

Question 7

In Regulation of Pyruvate Dehydrogenase:

What covalent modifications regulates pyruvate dehydrogenase?

Answer 7

• PD kinase phosphorylates E1, inactivating it
• PD phosphotase dephosphorylates E1, reactivating it

Question 8

In Regulation of Pyruvate Dehydrogenase:

What forms of allosteric control are present?

Answer 8

PD kinase:
* Inhibited by pyruvate and ADP
* Activated by Acetyl-CoA and NADH

PD phosphatase
* Activated by Ca2+

Question 9

State:

Tip to remember how regulation of pyruvate dehydrogenase works

Answer 9

1. Compunds that inhibit PD kinase, activate PDC
2. Compounds that activate PD kinase, inactivate PDC
3. Compounds that activate PD phosphatase, activate PDC

Question 10

Describe:

The Citric Acid Cycle

Answer 10

• Occurs in the mitochondrial matrix
• Performed in 8 steps
• Performed in two stages

Question 11

What are the two stages of the citric acid cycle?

Answer 11

1. Acetyle group is added to oxaloacetate converting it to citrate
2. Regeneration of oxaloacetate

Question 12

In the Citric Acid Cycle:

What does 1 Pyruvate molecule produce?

Answer 12

• 3 CO2 (one from PDC)
• 1 GTP
• 4 NADH (one from PDC)
• 1 FADH2

Question 13

In the Citric Acid Cycle:

For Step 1, state:
1. Reactants
2. Products
3. Enzyme that catalyzes reaction

Answer 13

1. Oxaloacetate and Acetyl-CoA
2. Citrate
3. Citrate Synthase

Question 14

In the Citric Acid Cycle:

For Step 2, state:
1. Reactants
2. Products
3. Enzyme that catalyzes reaction

Answer 14

1. Citrate
2. Isocitrate
3. Aconitase

Question 15

In the Citric Acid Cycle:

For Step 3, state:
1. Reactants
2. Products
3. Enzyme that catalyzes reaction

Answer 15

1. Isocitrate
2. α-Ketoglutarate
3. Isocitrate Dehydrogenase

Question 16

In the Citric Acid Cycle:

For Step 4, state:
1. Reactants
2. Products
3. Enzyme that catalyzes reaction

Answer 16

1. α-Ketoglutarate
2. Succinyl-CoA
3. α-Ketoglutarate Dehydrogenase

Question 17

In the Citric Acid Cycle:

For Step 5, state:
1. Reactants
2. Products
3. Enzyme that catalyzes reaction

Answer 17

1. Succinyl-CoA
2. Succinate
3. Succinyl-CoA Synthetase

Question 18

In the Citric Acid Cycle:

For Step 6, state:
1. Reactants
2. Products
3. Enzyme that catalyzes reaction

Answer 18

1. Succinate
2. Fumarate
3. Succinate Dehydrogenase

Question 19

In the Citric Acid Cycle:

For Step 7, state:
1. Reactants
2. Products
3. Enzyme that catalyzes reaction

Answer 19

1. Fumarate
2. Malate
3. Fumarase

Question 20

In the Citric Acid Cycle:

For Step 8, state:
1. Reactants
2. Products
3. Enzyme that catalyzes reaction

Answer 20

1. Malate
2. Oxaloacetate
3. Malate Dehydrogenase