cori cycle and Krebs cycle 2323232323.pptx

Cori cycle and Krebs cycle 2323232323.pptx

1. Carbohydrates Metabolism Overview

2. Sources of Glucose Glucose can be obtained from three primary sources: 1. Carbohydrate in Diet: Carbohydrates are sources for glucose of the body after meals. Excess glucose is stored in the form of glycogen in liver & skeletal muscles. 2. Glycogen , degradation. ( Glycogenlysis ): Glycogen (synthesized from glucose molecules) is stored in liver & skeletal muscles. In cases of fasting, liver glycogen is degraded to yield glucose for blood. In cases of muscular exercise , muscle glycogen is degraded to secure glucose for muscle as a source of energy. 3. Gluconeogenesis (Glucose Synthesis): It is the synthesis of glucose from noncarbohydrate sources (as some amino acids). It occurs in prolonged fasting

3. Catabolic pathways: For providing energy (ATP): Glycolysis Anaerobic Glycolysis: end product is lactate Aerobic Glycolysis: end product is pyruvate For providing synthetic products: Hexose monophosphate pathway (Produces NADPH & Ribose 5-Phosphate ) Glycogenlysis Anabolic pathways: Gluconeogenesis Glycogensis

4. The Six Carbohydrate Pathways

5. PENTOSE PATHWAY Lactate Carbohydrate metabolism pathway

6. A fter  glycolysis according to the presence of oxygen pyruvate have two different pathways. In an aerobic environment , it goes to the Krebs cycle and oxidative phosphorylation In an anaerobic environment it proceeds to l actic acid fermentation. Fate of Pyruvate after Glycolysis

7. In an anaerobic environment Lactic acid fermentation

8. Lactic acid fermentation does not need oxygen to proceed, although it can occur in its presence. During  lactic acid fermentation , pyruvate is converted into lactic acid, and the NADH produced during glycolysis is recycled. The net release of energy comes from glycolysis in the form of 2 ATP molecules . In an anaerobic environment it proceeds to lactic acid fermentation Lactic acid fermentation

9. Lactic acid fermentation Lactic acid fermentation happens  in the skeletal muscles . Pyruvate is converted to lactic acid by lactate dehydrogenase when oxygen is inadequate. Fatigue is brought on by lactic acid buildup in the muscles. It is an anaerobic fermentation

10. Energetics: Under anaerobic conditions, 2 ATP are synthesized . (8 – 6 (2NADH consumed to make lactate) =2 ATP) Under aerobic conditions, 8 are synthesized

11. M etabolic fate of lactate The Cori cycle is  a metabolic process and chemical pathway during which lactic acid produced in the muscles is converted to glucose by the liver and moved back to the muscles to be metabolized again . The Cori cycle is also called the lactate or lactic acid cycle

12. In an aerobic environment CITRIC ACID CYCLE/ KREBS CYCLE

13. Formation of acetyl Co-A from pyruvate Pyruvate (end product of glycolysis) is transported into the mitochondria for oxidative decarboxylation. In the mitochondrial matrix, pyruvate is converted to acetyl Co A by pyruvate dehydrogenase complex (multi enzyme complex) This reaction is irreversible Pyruvate dehydrogenase complex is composed of three enzymes & five coenzymes Coenzymes of the complex are derived from water soluble vitamins: Thiamine pyruphosphate , TPP (derived from thiamine, vitamin B1) NAD + (derived from niacin) FAD (derived from riboflavin) Lipoic acid Coenzyme A (derived from pantothenic acid)

14. Formation of acetyl Co-A from pyruvate

15. CITRIC ACID CYCLE Also called the Krebs cycle or the TCA cycle (tricarboxylic acid cycle ). It is the most important metabolic pathway for the energy supply to the body. About 65-70% of the ATP is synthesized in Krebs cycle. It involves the oxidation of acetyl CoA to CO2 & H2O. Location of the TCA cycle: Reactions of occur in mitochondrial matrix, in close proximity to the ETC. This cycle utilizes about two thirds of total oxygen consumed by the body. TCA cycle supplies energy and provides many intermediates required for the synthesis of amino acids, glucose , heme etc. Krebs cycle is the most important central pathway connecting almost all the individual metabolic pathways (either directly or indirectly).

16. CITRIC ACID CYCLE/ KREBS CYCLE

17. CITRIC ACID CYCLE/ KREBS CYCLE

18. Reactions: After Oxidative decarboxylation of pyruvate to acetyl CoA by pyruvate dehydrogenase complex 1. Formation of citrate : Krebs cycle starts with the condensation of acetyl CoA and oxaloacetate , catalysed by the enzyme citrate synthase . 2. Citrate is isomerized to isocitrate by the enzyme aconitase . 3. Formation of a- ketoglutarate : The enzyme isocitrate dehydrogenase (ICD) catalyses the conversion (oxidative decarboxylation) of isocitrate to a- ketoglutarate . The formation of NADH and the liberation of CO2 occur at this stage. 4. Conversion of a- ketoglutarate to succinyl CoA occurs through oxidative decarboxylation, catalysed by a- ketoglutarate dehydrogenase complex . second NADH is produced and the second CO2 is liberated . CITRIC ACID CYCLE/ KREBS CYCLE

19. 5. Formation of succinate : Succinyl CoA is converted to succinate by succinate Succinyl CoA synthetase . P hosphorylation of GDP to GTP occurs . GTP is converted to ATP by the enzyme nucleoside diphosphate kinase. GTP + ADP ATP + GDP 6. Conversion of succinate to fumarate : Succinate is oxidized by succinate dehydrogenase to fumarate. This reaction results in the production of FADH2 and not NADH. 7. Formation of malate : The enzyme fumarase catalyses the conversion of fumarate to malate with the addition of H2O. 8. Conversion of malate to oxaloacetate : Malate is then oxidized to oxaloacetate by malate dehydrogenase . The third and final synthesis of NADH occurs at this stage. The oxaloacetate regenerated can combine with another molecule of acetyl CoA, and continue the cycle. CITRIC ACID CYCLE/ KREBS CYCLE

20. CITRIC ACID CYCLE/ KREBS CYCLE

21. CITRIC ACID CYCLE/ KREBS CYCLE