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Metabolism of Nutrients in Liver

Explore comprehensive details on liver metabolism of key nutrients like carbohydrates, proteins, and lipids in this informative guide. Learn about glycolysis, gluconeogenesis, ketone bodies, and more.

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Metabolism of Nutrients in Liver

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  1. Metabolism of Nutrients in Liver AnusornCherdthong, PhD 137748 Applied Biochemistry in Nutritional Science Email: anusornc@kku.ac.th • E-learning: http://ags.kku.ac.th/eLearning/137748

  2. Introduction • Role of liver: • Biosynthesis • Metabolic regulation • Inactivation or detoxification • Secretion

  3. Liver metabolism Ruminant Riis (1983)

  4. Liver metabolism Non-ruminant Riis (1983)

  5. Carbohydrate metabolism • Major metabolism: • Glycolysis • Pentose phosphate pathway : PPP or hexosemonophosphate shunt : HMS • Gluconeogenesis • Glycogenolysis • Glycogenesis

  6. Glycolysis or Embden-Meyerhof Minus Pathway • Consisted of 11 reaction • Product: (1 glucose) • Pyruvate • 2 ATP McDonald et al. (2011)

  7. Krebs cycle • Occurred at mitocondria • Oxidation acetyl Co A—H2O, CO2 • Consisted 9 reactions • Product: 3 NADH 3, 1 FADH2 , 1GTP McDonald et al. (2011)

  8. Pentose phosphate pathway • Occurred at cytosol • Provided NADPH, ribose McDonald et al. (2011)

  9. Gluconeogenesis • glucokinase Km 10 mM (nonruminant) • Hexokinase KM 0.01-0.1mM(ruminant) • Substrate are glucogenic, amino acids, lactate, pyruvate, glycerol, propionate • Consisted of 3 reaction McDonald et al. (2011)

  10. Gluconeogenesis Substrates McDonald et al. (2011)

  11. Carbohydrate metabolism • Glycogenolysis • Lysis of glycogen when needed • Appeared in live and musle • End products are lactate or pyruvate • Required enzyme phosphorylase a

  12. Carbohydrate metabolism • Glycogenesis • synthesis of glycogen • Occurred at liver and muscle • Required enzyme glycogen synthetase

  13. Protein metabolism • Major metabolism • Amino acids degradation • Amino synthesis • Regulation of protein synthesis • Protein degradation

  14. Protein metabolism • Amino acids degradation • AA was used for energy source • End products are amino group and carbon skeleton • Ex: alanine degradation • Pyruvate, aspatice acid • Oxaloacetate, glutamate • -ketoglutarate • 2 reactions are deamination, carbon skeletal pathway

  15. Utilization of C skeleton McDonald et al. (2011)

  16. McDonald et al. (2011) • Urea cycle • 1 urea/ 4 ATP • Excrete via urine

  17. Protein metabolism • Amino synthesis • Biosynthesis of non-essential amino acids • Required glutamate dehydrogenase • NADP as Co A • ATP • Re-used ammonia for synthesis • Consisted of oxidation and tranamination reaction

  18. Protein metabolism • Regulation of protein synthesis • Control by RNA content in muscle, ATP and initiation process • Occurred ribosomes • high synthesis rate when fasting

  19. Protein metabolism • Protein degradation • Enzymes: endoenzymesand exoenzymes • Endoenzymes: cathepsins B and D—short chain polypeptide • Exoenzymes---degrade polypeptide to AA • Cathepsins B-- albumin, ribonuclease andcytochrome C • Cathepsins D---haemoglobin • Aminopeptidease D andalanineaminopeptidases degrade peptide at N-terminal

  20. Lipid metabolism • Major metabolism • Lipolysis • Glycerol lysis • Fatty acid biosynthesis • Biosynthesis of triacylglycerols • Biosynthesis of cholesterol • Biosynthesis of glycerol • Ketone bodies

  21. Lipid metabolism • Lipolysis • Required glycerol 3-phosphate • Major reaction is -oxidation • Occurred in mitochondria • Acyl Co A form • Carnitine transfer Acyl Co A across inner mitochondreia and need Carnitineacyltransferase I

  22. Lipid metabolism • Lipolysis • -oxidation—degrade FA on C beta • 4 step of -oxidation • Dehydrogenation 1 • Hydration • Dehydrogenation 2 • Thiolytic cleavage • 2 atom C are end product

  23. Lipid metabolism • Glycerol lysis • For energy source • Start from fructose-1,6 diphosphate—glycolysis—pyruvate—TCA • 44 ATP/ 2 Glycerol

  24. Lipid metabolism • Fatty acid biosynthesis • Occurred when sufficient energy, high Acetyl CoA • Require NADPH • Store as tryacylglecerol • Consisted 2 sinthesis systems • De novo synthesis • Saturated FA with more than 16 C

  25. Lipid metabolism • Biosynthesis of triacylglycerols • Occurred when more CHO • Substrates are FA (Fatty acyl-Co A ) and glycerol (Glycerol-3-phosphate) • Diacylglycerol-3-phosphate was found in reaction • 1,2-Diacylglycerol+Fatty acyl-Co A =triacylglycerols

  26. Lipid metabolism • Biosynthesis of cholesterol • Normally found in Liver • LDL carrier cholesterol to other organs • 3 step of biosynthesis: • Synthesis mevalonate fromacetyl Co A • Synthesis squalene frommevalonate • Synthesis cholesterol from squalene

  27. Lipid metabolism • Biosynthesis of glycerol • Synthesis from glucose via glycolysis • Start with dihydroxyacetone phosphate---glyceral- 3 –phosphate---phosphodiglyceride---diacylglycerol---triacylglycerol

  28. Lipid metabolism • Ketone bodies • Occurred when starvation • Namely: Acetone, acetoacetate and D--hydroxybutyrate • Ketonebodies were transfer to organ for energy • Enzyme require: thiolase,HMG-Co A synthase,HMG-Co A lyase, D--hydroxybutyratedehydrogenase andacetoacetatedecarboxylase • Ketosis: high accumulated of KB

  29. 1 2 3 4 Conclusion Metabolism of nutrient in liver Carbohydrate metabolism : Glycolysis, PPP, Gluconeogenes, Glycogenolysis and Glycogenesis Protein metabolism : AA metabolism, urea cycle, protein metabolism Lipid metabolism : Lipolysis, glycerol lysis, fatty acid, triacylglycerols, cholesterol Ketonebodies

  30. Thank you!

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