Leyland 10 Gluconeogenesis

Question 1

What happens if we run out of glycogen?

Answer 1

liver glycogen for 8-12 hours
• muscle glycogen cannot maintain plasma glucose
• glucose 6-phosphate cannot be released from muscle cells

Question 2

GLUCONEOGENESIS:

Answer 2

• Synthesis of glucose from (mainly) noncarbohydrate precursors

Question 3

GLUCONEOGENESIS

occurs:

Answer 3

• in the liver (& kidney cortex)
• when runs out (eg overnight fast)
  • some tissues are totally dependent on glucose (rbc, wbc, kidney medulla, lens of eye)

Question 4

Gluconeogenesis is NOT a reversal of glycolysis:

Answer 4

Alternative reactions must occur to overcome the irreversible reactions in glycolysis
Reversal of glycolysis DG0’ = +20kJ/mol
Gluconeogenesis DG0’ = -11kJ/mol

Question 5

Glycolysis enzymes:

Answer 5

• Hexokinase
• Phosphofructokinase
• Pyruvate kinase

Question 6

Gluconeogenesis enzymes:

Answer 6

Glucose-6-phosphatase
Fructose -1,6-bisphosphate
Pyruvate carboxylase
PEP carboxykinase

Question 7

Reactions of glycolysis are bypassed

x4

Answer 7

1. pyruvate carboxylase (PC):
2. phosphoenolpyruvate carboxykinase (PEPCK):
3. glucose 6-phosphatase:
4. fructose 1,6-bisphosphatase:

Question 8

pyruvate carboxylase (PC)

Answer 8

pyruvate + CO2 + ATP + H2O à
oxaloacetate + ADP + Pi + 2H

Reactions of glycolysis are bypassed

Question 9

phosphoenolpyruvate carboxykinase (PEPCK):

Answer 9

oxaloacetate + GTP + 2H+ à
phosphoenolpyruvate + GDP + CO2
Reactions of glycolysis are bypassed

Question 10

glucose 6-phosphatase:

Answer 10

glucose 6-P + H2O à glucose + Pi

Reactions of glycolysis are bypassed

Question 11

fructose 1,6-bisphosphatase:

Answer 11

fructose 1,6-bisP + H2O à fructose 6-P + Pi

Reactions of glycolysis are bypassed

Question 12

Gluconeogenic substrates

Answer 12

• Lactate from anaerobic glycolysis
  • Amino acids
  • Glycerol from TAGs

Question 13

THE CORI CYCLE

Answer 13

• Lactate formed by active muscle (anaerobic glycolysis)
• In liver, pyruvate converted to glucose (gluconeogenesis).
- Liver restoring glucose used by active muscle

Question 14

Fatty acids are NOT a source of precursors for gluconeogenesis

Answer 14

• The reaction catalysed by pyruvate dehydrogenase is irreversible
• Cycling of acetyl CoA through the citric acid cycle results in the loss of 2 carbon atoms as CO2

Question 15

Regulation of gluconeogenesis

Answer 15

Glycolysis and gluconeogenesis are reciprocally regulated