Glycolysis and gluconeogenesis

Question 1

What happens during glycolysis?

Answer 1

1 molecule of glucose is broken down via a series of reactions to yield 2 molecules of pyruvate and 2ATP

Question 2

What happens during gluconeogenesis?

Answer 2

Synthesis of glucose from non-CHO sources. Requires E from fat metabolism and a C source

Question 3

Which 3 enzymes regulate glycolysis?

Answer 3

Hexokinase, phosphofructokinase, pyruvate kinase

Question 4

What are the 4 enzymes which regulate gluconeogenesis?

Answer 4

Glucose-6-phosphatase, fructose-1,6-bisphosphate, PEP carboxylase, pyruvate carboxylase

Question 5

What happens in the first regulatory step?

Answer 5

• Hexokinase is stimulated by increased glucose conc.
• PFK inhibited, conc. glucose-6-phosphate increases which inhibits hexokinase and stimulates glucose-6-phosphatase so gluconeogenesis occurs

Question 6

What happens in the 2nd regulatory step?

Answer 6

• F-1,6-BPase inhibited - AMP (low cell E)
• F-1,6-BPase stimulated - citrate
• PFK inhibited - ATP, low pH, citrate, low glucose
• PFK stimulated - AMP, F-2,6-BP
• PFK2 has a dual kinase and phosphatase action
• When glucose is high, insulin dephosphorylates PFK2, PFK2 converts F-6-P to F-2,6-BP, stimulating PFK1 and inhibiting F-1,6-BPase
• When glucose is low, glucagon high, PFK2 phosphorylated, less F-2,6-BP, PFK1 inhibited and F-1,6-BPase stimulated

Question 7

What happens in the 3rd regulatory step?

Answer 7

• Pyruvate kinase activated - F-1,6-BP, insulin
• Pyruvate kinase inhibited - ATP, alanine, acetyl CoA, glucagon
• PEP carboxykinase activated - acetyl CoA
• Pyruvate carboxylase activated - acetyl CoA
• Pyruvate carboxylase inhibited - ADP
• OAA too lrg to move out of mitochondrial membrane so is converted to malate, enters cytosol where is converted back to OAA