BIOCHEMISTRY – GLUCONEOGENESIS (DETAILED HIGH-YIELD NOTES)
Definition:
Gluconeogenesis is the formation of glucose from non-carbohydrate sources.
Sources:
- Lactate
- Amino acids
- Glycerol
Location:
- Liver (main), Kidney (minor)
- Occurs in mitochondria, cytoplasm, ER
Purpose:
- Maintain blood glucose during fasting/starvation
Key Steps (Bypass of Glycolysis):
1. Pyruvate → Oxaloacetate (Pyruvate carboxylase, requires biotin)
2. Oxaloacetate → PEP (PEPCK)
3. Fructose-1,6-bisphosphate → Fructose-6-P (Fructose-1,6-bisphosphatase, rate-limiting)
4. Glucose-6-phosphate → Glucose (Glucose-6-phosphatase)
Energy Requirement:
- 4 ATP, 2 GTP, 2 NADH
Regulation:
- Glucagon activates
- Insulin inhibits
Clinical:
- Fasting → increased gluconeogenesis
- Diabetes → increased glucose production
- Alcoholism → decreased gluconeogenesis → hypoglycemia
Key Points:
- Opposite of glycolysis
- Occurs mainly in liver
- Muscle lacks glucose-6-phosphatase
