metabolismofcarbohydrates.ppt for nusring students
- 4. The study of synthesis (Anabolism) and degradation (catabolism) of biomolecules is biochemically termed as metabolism. Metabolism of carbohydrate
- 5. Structural maintenance Support of growth Production of secretions Building of nutrient reserves Anabolism
- 6. Breakdown of nutrients to provide energy (in the form of ATP) for body processes Nutrients directly absorbed Stored nutrients Cells break down excess carbohydrates first, then lipids, finally amino acids if energy needs are not met by carbohydrates and fat 40% of the energy released in catabolism is captured in ATP, the rest is released as heat Catabolism
- 7. Carbohydrate Metabolism Primarily glucose Fructose and galactose enter the pathways at various points All cells can utilize glucose for energy production Liver is central site for carbohydrate metabolism
- 8. Glucose Metabolism Four major metabolic pathways: Immediate source of energy Pentose phosphate pathway Glycogen synthesis in liver/muscle Precursor for triacylglycerol synthesis
- 11. Glycolysis Sequence of reactions that converts glucose into pyruvate Relatively small amount of energy produced Glycolysis reactions occur in cytoplasm Does not require oxygen Glucose 2 Pyruvate Lactate (anaerobic) Acetyl-CoA (TCA cycle)
- 12. Glycolysis pathway: Oxidation of glucose to Pyruvate +water+ NADH2 in steps wise (10 steps). It take place in all cells, for the break down of glucose to provide energy. *Glycolysis pathway occurs in most cell in the presences of oxygen and called (aerobic glycolysis) An-aerobic glycolysis: occurs in the completely absent of oxygen or partial deficiency of oxygen.
- 13. An aerobic glycolysis found in: 1- Red blood cells (no mitochondria) 2-Labor (partial deficiency of oxygen) 3-Exercise muscle (partial deficiency of oxygen) 4-Cancer cells
- 14. Glycolysis Glucose + 2 ADP + 2 Pi 2 Pyruvate + 2 ATP + 2 H2O
- 15. First Reaction of Glycolysis Traps glucose in cells (irreversible in muscle cells)
- 16. Glycolysis - Summary Glucose (6C) 2 Pyruvate (3C) 2 ATP 2 ADP 4 ADP 4 ATP 2 NAD 2 NADH + H
- 17. Pyruvate Metabolism Three fates of pyruvate: Conversion to lactate (anaerobic) Conversion to alanine (amino acid) Entry into the TCA cycle via pyruvate dehydrogenase pathway (create ATP)
- 18. Pyruvate Metabolism Three fates of pyruvate: Conversion to lactate (anaerobic) Conversion to alanine (amino acid) Entry into the TCA cycle via pyruvate dehydrogenase pathway
- 19. Anaerobic Metabolism of Pyruvate to Lactate Problem: During glycolysis, NADH is formed from NAD+ Without O2, NADH cannot be oxidized to NAD+ No more NAD+ All converted to NADH Without NAD+ , glycolysis stops
- 20. Anaerobic Metabolism of Pyruvate Solution: Turn NADH back to NAD+ by making lactate (lactic acid) COO C O CH3 COO HC OH CH3 Lactate Pyruvate Lactate dehydrogenase NADH + H+ NAD+ (oxidized) (reduced) (oxidized) (reduced)
- 21. Anaerobic Metabolism of Pyruvate ATP yield Two ATPs (net) are produced during the anaerobic breakdown of one glucose The 2 NADHs are used to reduce 2 pyruvate to 2 lactate Reaction is fast and doesnt require oxygen Lactate can be transported by blood to liver and used in gluconeogenesis
- 22. Cori Cycle Lactate is converted to pyruvate in the liver
- 23. Pyruvate Metabolism Three fates of pyruvate: Conversion to lactate (anaerobic) Conversion to alanine (amino acid) Entry into the TCA cycle via pyruvate dehydrogenase pathway
- 24. Pyruvate metabolism Convert to alanine and export to blood COO C O CH3 COO HC NH3 + CH3 Alanine amino transferase (AAT) Alanine Pyruvate Glutamate -Ketoglutarate Keto acid Amino acid
- 25. Pyruvate Metabolism Three fates of pyruvate: Conversion to lactate (anaerobic) Conversion to alanine (amino acid) Entry into the TCA cycle via pyruvate dehydrogenase pathway
- 26. Pyruvate Dehydrogenase Complex (PDH) Prepares pyruvate to enter the TCA cycle Electron Transport Chain TCA Cycle Aerobic Conditions
- 27. TCA Cycle In aerobic conditions TCA cycle links pyruvate to oxidative phosphorylation Occurs in mitochondria Generates 90% of energy obtained from food Oxidize acetyl-CoA to CO2 and capture potential energy as NADH (or FADH2) and some ATP Includes metabolism of carbohydrate, protein, and fat
- 29. TCA Cycle - Summary Acetyl CoA 3 NAD 3 NADH + H 1 FAD 1 FADH2 1 ADP 1 ATP 2 CO2
- 30. Electron transport chain (E.T.C): This pathway is found in inner mitochondria matrix, energy rich molecules, such as glucose or fatty acids are metabolized by series of oxidation reaction ultimately yielding co2 and H20.
- 32. Total ATP from Glucose Anaerobic glycolysis 2 ATP Aerobic metabolism glycolysis + TCA 38 ATP from 1 glucose molecule
- 33. Energy production from complete oxidation of glucose :- 2 ATP (glycolysis) 2 ATP 2NADH2 (glycolysis) 23 = 6 ATP
- 34. 2NADH2 (Pyruvate dehydrogenase) E.T.C 23 = 6 ATP 2 Acetyl-coA(212 ATP) 24 ATP
- 35. Net energy from aerobic glycolysis: 2 ATP + 6 ATP + 6 ATP + 24 ATP = 38 ATP
- 37. Pentose Phosphate Pathway Secondary metabolism of glucose Produces NADPH Similar to NADH Required for fatty acid synthesis Generates essential pentoses Ribose Used for synthesis of nucleic acids
- 39. Energy Storage Energy from excess carbohydrates (glucose) stored as lipids in adipose tissue Determined by ATP:ADP ratios High ATP, acetyl-CoA goes to fatty acid synthesis Low ATP, acetyl CoA enters TCA cycle to generate MORE ATP
- 41. Liver Use glycogen to export glucose to the bloodstream when blood sugar is low Glycogen stores are depleted after approximately 24 hrs of fasting (in humans) Glycogenesi s
- 42. Glycogenesis Skeletal muscle More muscle than liver, therefore more glycogen in muscle, overall Use glycogen (i.e., glucose) for energy only (no export of glucose to blood) Use already-made glucose for synthesis of glycogen
- 43. Fates of Glucose Fed state Storage as glycogen Liver Skeletal muscle Storage as lipids Adipose tissue Fasted state Metabolized for energy New glucose synthesized Synthesis and breakdown occur at all times The relative rates of synthesis and breakdown change
- 44. Fasting Situation Where does required glucose come from? Glycogenolysis Lipolysis Proteolysis Breakdown or mobilization of glycogen stored by glucagon Glucagon - hormone secreted by pancreas during times of fasting Mobilization of fat stores stimulated by glucagon and epinephrine Triglyceride = glycerol + 3 free fatty acids Glycerol can be used as a glucose precursor The breakdown of muscle protein with release of amino acids Alanine can be used as a glucose precursor
- 45. Low Blood Glucose Proteins Broken Down Insulin Pancreas Muscle Adipose Cells Glycogen Glycerol, fatty acids released Glucose released In a fasted state, substrates for glucose synthesis (gluconeogenesis) are released from storage
- 46. Gluconeogenesis Necessary process Glucose is an important fuel Central nervous system Red blood cells Not simply a reversal of glycolysis Insulin and glucagon are primary regulators
- 47. Gluconeogenesis Synthesis of glucose from non-carbohydrate precursors during fasting. Glycerol Amino acids Lactate Pyruvate Propionate There is no glucose synthesis from fatty acids Supply carbon skeleton