Met 1: TCA Cycle

Question 1

What are the starting and end products of TCA cycle?

*2 ways to think about this

Answer 1

• Start with acetyl-coA, end with CO2
• Or start with citrate, end with oxaloacetate

Question 2

What is made during TCA cycle?

Answer 2

NADH, FADH2, GTP (high energy intermediates)

Question 3

Name 3 inputs for TCA cycle

Answer 3

1. Pyruvate from glucose
2. Acetyl-coA from fatty acids
3. Amino acids (enter at different points)

Question 4

Where and when does TCA cycle occur?

Answer 4

Where: inner mitochondrial matrix

When: during fed states

Question 5

What is the key regulatory step of TCA cycle?

Answer 5

Conversion of pyruvate into acetyl-coA by pyruvate dehodrogenase

Question 6

What is the effect of NADH and acetyl-coA on pyruvate dehydrogenase?

Answer 6

• Pyruvate dehydrogenase is TCA enzyme
  
  • Should be active during fed or low energy states
• NADH (high energy) and acetyl-coA (downstream product) both inhibit pyruvate dehydrogenase

Question 7

What is the effect of calcium on pyruvate dehydrogenase?

Answer 7

• Pyruvate dehydrogenase is TCA enzyme
  
  • Should be active in low energy states
• Active muscles will both have high calcium and need more energy
• So, Ca activates pyruvate dehydrogenase

Question 8

What is the effect of insulin on pyruvate dehydrogenase?

Answer 8

• Pyruvate dehydrogenase is a TCA enzyme
  
  • Should be active during fed state (high insulin)
• Insulin dephosphorylates enzymes
• So, dephosphorylation of PDH by insulin must ACTIVATE it

Question 9

When in carbohydrate metabolism have all 6 carbons from glucose been fully oxidized?

Answer 9

• Glucose is broken down to 3 sugar compounds (pyruvate) during glycolysis
• Pyruvate -> acetyl-coA loses one carbon as CO2
• TCA loses the other two carbons as CO2