Lecture 3: Gluconeogenesis

Question 1

What is the purpose of synthesizing glucose?

Answer 1

• During fasting or starvation
• RBCs and brain need glucose
• interconvert metabolites for cell’s needs

Question 2

Occurrences and location of glycolysis and gluconeogenesis:

Answer 2

• Glycolysis: All cells; especially brain, muscles, and RBCs
• Gluconegenesis: Liver and Kidney
• Both take place in cytosol

Question 3

What is the role of biotin?

Answer 3

• 1 carbon carrier
• attached to a Lys, which is then attached to pyruvate carboxylase
• requres mitochondrial transport

Question 4

What is the expense of gluconeogenesis?

Answer 4

-Costs 4 ATP, 2 GTP, and 2 NADH.

Question 5

Can animals produce glucose from sugars, proteins, and fatty acids?

Answer 5

-YES:
~sugars: pyruvate , lactate (doesnt require mitochondria), or oxaloacetate.
~proteins: from amino acids and can be converted to TCA intermediates or gluconeogenic amino acids.

-NO:
~Fatty acids: degradation produces Acetyl-CoA

Question 6

Fates of pyruvate: (x3)

Answer 6

1. 3 CO2 + 2 H2O
2. Lactate
3. Ethanol

Question 7

What is the purpose of fermentation?

Answer 7

• Anaerobic process that regenerates NAD+ for glycolysis.

- Only source of ATP for cells that lack mitochondria.

Question 8

Characteristics of lactate dehydrogenase:

Answer 8

• reversible
• occurs in vertebrates under anaerobic conditions.
• increases [H+] and [lactate] in muscle tissue
• strenuous exercise.

Question 9

Characteristics of ethanol fermentation:

Answer 9

• occurs in yeast under anaerobic conditions.

- Two step irreversible process.

Question 10

Name a common acetaldehyde carrier:

Answer 10

-2-carbon carrier.
Thiamine Pyrophosphate (TPP)

Question 11

Describe the Cori cycle:

Answer 11

• interconversion of glucose and lactate between muscle and tissue.
• under vigorous anaerobic exercise.

-Muscle:
~glycolysis converts glucose to pyruvate.
~pyruvate to lactate; which regenerate NAD+ for glycolysis.
~Lactate transported to liver via blood.

-Liver:
~Lactate to pyruvate.
~Pyruvate to glucose
~glucose returns to muscle for glycolysis and ATP production.