LECTURE 20 - ANAEROBIC FERMENTATION & TCA CYCLE

Question 1

Describe the mechanism of ATP production by oxidative phosphorylation

Answer 1

1) ATP is harvested from the oxidation of NADH & FADH2 using O2
– Occurs in the mitochondrial inner membranes
2) Electrons from NADH & FADH2 are transferred to O2 (OXIDATION)
3) The electron transfer is coupled with the transfer of protons across the membrane, generating the proton-motive force.
– Proton gradient
4) ATP synthase produces ATP using the proton-motive force

Question 2

Identify the end products of glycolysis in humans under anaerobic conditions

Answer 2

Output = 2 Lactate
Energy Harvested = 2 ATP

Question 3

Identify the end products of glycolysis in yeast under anaerobic conditions

Answer 3

Ethanol
– Can be converted to energy once oxygen is available

Question 4

What is the energy output from glycolysis under aerobic conditions?

Answer 4

Much higher than the energy output under anaerobic conditions (~32 ATP)

Question 5

What is the energy output from glycolysis under anaerobic conditions?

Answer 5

Much lower than the energy output under aerobic conditions (~2 ATP)

Question 6

Describe the physiological consequences of the excessive production of lactate

Answer 6

Overproduction or underutilization of lactate may decrease blood pH (lactic acidosis)

Question 7

List the various sources of Acetyl-CoA

Answer 7

Acetyl-CoA is ketogenic and can be produced from:
- Glucose
- Fatty acids
- Some amino acids

Question 8

List the various fates of Acetyl-CoA

Answer 8

1. Fuel of TCA cycle
   – uses Acetyl-CoA (CoA as a cofactor, acetyl as fuel)
2. Material for fatty acid synthesis and ketogenesis
   – Can create fatty acids for storage
   – Can make ketone bodies
   – Can make Cholesterol

Question 9

Describe the uses of TCA cycle intermediates in biosynthesis

Answer 9

Intermediates in the TCA cycle are critical building blocks for gluconeogenesis and amino acid synthesis (neurotransmitters)

Question 10

What reaction(s) can Citrate be used in?

Answer 10

TCA cycle
Fatty Acid & Cholesterol synthesis

Question 11

What reaction(s) can alpha-ketoglutarate be used in?

Answer 11

TCA cycle
Amino Acid synthesis

Question 12

Describe the purpose of anaplerotic reactions

Answer 12

Anaplerotic (“filling up”) reactions replenish TCA cycle intermediates

Question 13

What is the most important anaplerotic reaction?

Answer 13

Pyruvate –> oxaloacetate
catalyzed by pyruvate carboxylase

Question 14

Explain the rationale of the use of triheptanoin in pyruvate carboxylase deficiency

Answer 14

• When there is a pyruvate carboxylase deficiency, cannot replenish the TCA cycle
• Can be treated with triheptanoin (triglyceride with C7 fatty acid), which are converted to succinyl-CoA
  – When there is an odd number of carbons in a fatty acid, succinyl-CoA can be generated
  – Succinyl-CoA is a TCA cycle intermediate that can be replenished by odd-chain fatty acids