4C- Tricarboxylic Acid Cycle

Question 1

Gives the general process of the TCA cycle and the molecules that feed into it and leave it

Answer 1

Used:

• Acetyl-CoA
• 3 NAD+
• 1 FAD+
• GDP + Pi
• 2 H2O

Produced:

• 3 NADH + H
• 1 FADH2
• 2 CO2
• 1 GTP

Question 2

What is a regulator of isocitrate dehydrogenase?

Answer 2

Inhibitors: ATP

Activators: Ca++, ADP

Question 3

What is a regualtor of α-ketoglutarate dehydrogenase?

Answer 3

Inhibitors: succinyl-CoA, NADH

Activators: Ca++

Question 4

What is a regulator of pyruvate dehydrogenase?

Answer 4

Inhibitors: ATP, acetyl-CoA, NADH, fatty acids

Activators: AMP, CoA, NAD+, Ca++

Question 5

Give a summary of activators, inhibitors and products of the TCA cycle

Answer 5

Question 6

What are the 5 sources of acetyl-CoA?

Answer 6

fatty acids

ketone body

glucose

pyruvate

ethanol

Question 7

How is acetyl-CoA synthesized from pyruvate?

Answer 7

the pyruvate dehydrogenase complex is the enzyme mediator

Question 8

How are intermediates of the TCA cycle replenished?

Answer 8

Question 9

How does thiamine (B1) deficiency affect the TCA?

Answer 9

B1 is requried for the pyruvate dehydrogenase complex to work to convert pyruvate–> acetyl-CoA

deficiency = decreased acetyl-coa, impairment of TCA

Question 10

How does alcoholism affect the TCA cycle?

Answer 10

A central role in the toxicity of alcohol may be played by acetaldehyde itself. Although the liver converts acetaldehyde into acetic acid, it reaches a saturation point where some of it escapes into the blood stream. The accumulated acetaldehyde exerts its toxic effects by inhibiting the mitochondria reactions and functions. The alcoholic is a victim of a vicious circle; a high acetaldehyde level impairs mitochondria function, metabolism of acetaldehyde to acetic acid decreases, more acetaldehyde accumulates, and causes further liver damage–hepatitis and cirrhosis.