Revision - CHO Metabolism PDF

Revision on CHO metabolism 1. A pure anabolic pathway is: - Glycogenesis - Gluconeogenesis 2. A pure catabolic pathway is; - Glycolysis – Oxidative decarboxylation – Krebs cycle - HMP shunt – Uronic acid pathway – Glycogenolysis 3. Amphibolic pathway is Krebs cycle 4. Aerobic glycolys...

Revision on CHO metabolism 1. A pure anabolic pathway is: - Glycogenesis - Gluconeogenesis 2. A pure catabolic pathway is; - Glycolysis – Oxidative decarboxylation – Krebs cycle - HMP shunt – Uronic acid pathway – Glycogenolysis 3. Amphibolic pathway is Krebs cycle 4. Aerobic glycolysis of glucose gives 6 – 8 ATP - Anaerobic glycolysis of glucose gives 2 ATP - Complete oxidation of one molecule of glucose aerobically gives 36 – 38 ATP - Oxidative decarboxylation of 2 Molecules of pyruvate gives 6 ATP - Oxidation of one molecule of acetyl CoA by Krebs gives 12 ATP 5. Examples of substrate level phosphorylation include; - In glycolysis 2 examples (by phosphoglycerate kinase and pyruvate kinase) - In Krebs cycle (by succinate thiokinase) 6. A coenzyme required by; - HMP shunt is NADP - Glyceraldhyde-3-phosphate DH is NAD - Succinate DH is FAD 7. Uronic acid pathway is important for production of Glucuronic acid in the form of UDP-glucuronic acid (used for detoxification reactions – Conjugation reactions – Synthesis of vitamin C in animals not in humans) 8. HMP shunt is important in production of NADPH+H and ribose-5-phosphate. 9. The key enzymes of; - Glycolysis (Hexokinase and glucokinase – Phosphofructokinase1 – Pyruvate kinase) - Krebs (citrate synthase – Isocitrate synthase – α ketoglutarate DH) - HMP shunt (Glucose-6-phosphate DH) - Glycogenesis (Glycogen synthase) - Glycogenolysis (Glycogen phosphorylase) - Gluconeogenesis (Pyruvate carboxylase – Phosphoenol pyruvate carboxykinase – Fructose 1, 6 biphosphatase – Glucos-6-phosphatase) 1 10. Requirements for glycogenesis: Glycogen synthase – UDP-glucose – Branching enzyme – Glycogen primer. 11. Requirements for glycogenolysis: Glycogen phosphorylase – inorganic phosphate – Glucan transferase – Debranching enzyme. 12. Glycogenolysis in the liver gives free glucose due to the presence of glucose-6- phosphatase enzyme in liver 13. Glycogenolysis in muscles can't give free glucose due to the absence of glucose-6- phosphatase enzyme in the muscles. 14. Cycles that occur completely in the cytoplasm include glycolysis, oxidative decarboxylation, HMP shunt, uronic acid pathway, glycogenesis and glycogenolysis. 15. Cycle that occurs completely in the mitochondria is Krebs cycle 16. Cycle that occurs both in mitochondria and cytoplasm is gluconeogenesis. 17. Glycogen phosphorylase breaks only α a- 4 glucosidic bond – breaks by phosphorylysis (breakdown by addition of inorganic phosphate). 18. For synthesis of glucose from glycerol it must be converted first to dihydroxyacetone, while for synthesis from propionol it must be first converted to succinyl CoA. 19. Fructose 2, 6 by phosphate is fromed from fructose-6-phosphate by phosphofructokinase 2 – it stimulates glycolysis by stimulating phosphofructokinase 1 and inhibits gluconeogenesis by inhibiting fructose 1, 6 biphosphatase. 20. Fanconi syndrome is characterized by decreased renal tubular reabsorption of glucose, amino acids and phosphate leading to glucosuria, aminoaciduria and phosphaturia. 21. Oxidative decarboxylation of pyruvate to acetyl CoA occurs by pyruvate DH complex that needs 5 coenzymes (NAD – FAD – COASH – TPP – Lipoic acid) – Also oxidative decarboxylation of alpha ketoglutarate to succinyl CoA occurs by alpha ketoglutarate DH complex that needs the same 5 coenzymes. 22. Glycolysis in RBCs is characterized by (anaerobic – ends by lactate – gives only 2 ATP – can produce 2, 3 biphosphoglycerate – occurs independent of insulin hormone). 2 23. The normal fasting blood glucose (70 – 110 mg/dl) – 2 hours PP (up to 140 mg/dl) – random blood glucose (up to 140 mag/dl) – hypoglycemia occurs when the blood glucose level is decreased below 60 mg/dl. 24. The normal renal threshold is 180 mg/dl. 25. The action of glucokinase and hexokinase on glucose gives glucose-6-phosphate 26. The action of fructokinase on fructose gives fructose-1-phosphate while the action of hexokinase on fructose gives fructose-6-phosphate. 27. The action of galactokinase on galactose gives galactose-1-phosphate while the action of hexokinase on galactose gives galactose-6-phosphate. 3