Protein digestion

• Protein digestion in the stomach

  Where: stomach

  Secretion source: chief cells

  Enzyme: pepsinogen to pepsin

  Substrate: large polypeptides

  Products: smaller polypeptides
• Protein digestion in the duodenum

  Where: duodenum

  Secretion source: pancreas

  Enzyme: trypsinogen to trypsin, exopeptidase

  Substrate: larger polypeptides, smaller polypeptides

  Products: smaller polypeptides, dipeptides
• Protein digestion in the intracellular in the membranes of the microvilli cells

  Where: cells

  Enzyme: dipeptidase

  Substrate: dipeptides

  Products: amino acids
• Protein digestion:

  large polypeptides are broken down into smaller polypeptides, in the stomach by pepsin, which was secreted from chief cells as pepsinogen.

  In the extracellular duodenum large polypeptides are broken down by trypsin (secreted by the pancreas as trypsinogen) into smaller polypeptides, which are broken down by exopeptidase into dipeptides.

  In the intracellular duodenum, dipeptides are broken down by dipeptidase into amino acids.

  They travel to the ileum for absorption
• Autolysis - self digestion of proteins in your own cells
• Where are the products of protein digestion absorbed?

  In the ileum into the blood
• uses of protein once digested:

  • amino acids are absorbed into the cells for protein synthesis
  • excess are deaminated in the liver into keto acid (can be respired) and urea (excreted)