Protein Digestion 111309 2 slide

Protein Digestion 111309 2 slide - PROTEIN DIGESTION &...

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1 P ROTEIN D IGESTION & A BSORPTION ( PG . 189-194) Lia M. Nightingale, Ph.D. P ROTEINS EPTIDES We consume ~100 grams of exogenous protein per day from: Animal products (meat, dairy, etc.) Plant proteins (legumes, nuts, etc.) We get ~200 grams of endogenous protein from: Digestive enzymes Sloughed cells Digested by efficient proteases Lys Lys Lys Gly Gly Val His Met Phe Only ~10 grams lost/day in feces.
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2 P ROTEIN D IGESTION - M OUTH No protein digestion occurs in the mouth P ROTEIN D IGESTION - S TOMACH HCl is released from parietal cells in response to gastrin 1. structure of protein 2. Converts pepsinogen (inactive) to pepsin (active) HCl or Pepsin Removes 46 amino acids to activate Pepsinogen Pepsin
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3 P ROTEIN D IGESTION - S TOMACH Pepsin is an endopeptidase Lys Tyr Lys Trp Val Met His Trp Phe Results in large polypeptides, oligopeptides, & free amino acids. Digests internal peptide bonds P ROTEIN D IGESTION - SI Chyme release into SI stimulates release of secretin & CCK (cholecystokinin) Secretin & CCK stimulate release of bicarbonate , water, from pancreas Neutralizes stomach acid Inactive enzymes
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4 P ANCREATIC Z YMOGENS Enterokinase * or Trypsin Trypsinogen Trypsin Trypsin Chymotrypsinogen Chymotrypsin Trypsin Procarboxypeptidase Carboxypeptidase Trypsin Proelastase Elastase *A brushborder enzyme in SI P ANCREATIC E NZYMES - E NDOPEPTIDASES Trypsin Chymotrypsin Elastase Collagenase Digests internal peptide bonds Digests protein in collagen Digests protein in elastin Products of pancreatic endopeptidase digestion: peptides and amino acids
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5 P ANCREATIC E NZYMES - E XOPEPTIDASES Digests external peptide bonds Digests protein from the carboxy terminal Carboxypeptidase C R 2 H C O N H C R 3 H C
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Protein Digestion 111309 2 slide - PROTEIN DIGESTION &...

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