Digestion & Absorption

• Digestion, Starch:

  • Starch is hydrolysed into maltose by amylase.
  • Amylase is made in the salivary glands, pancreas and works in the duodenum.
  • Maltose is hydrolysed into alpha glucose by maltase.
  • Maltase is made in the ileum lining.
• Absorption, Starch:

  • Na+ is moved from the epithelium into the blood by active transport.
  • Na+ diffuses into the cell.
  • Glucose is moved into the epithelium by co-transport.
  • Glucose is moved through a channel into the blood by facilitated diffusion.
• Digestion, Protein:

  • Endopeptidases. Hydrolyse internal peptide bonds, turning long polypeptides into shorter polypeptides. It is made in the stomach and pancreas.
  • Exopeptidases. Hydrolyse peptide bonds at terminal ends, forming single amino acids or dipeptides. It is made in the pancreas.
  • Dipeptidases. Dipeptides are hydrolysed to single amino acids. It is made in the ileum lining.
• Absorption, Protein:

  • Na+ is actively transported out the epithelium into the blood.
  • Na+ diffuses into the cell.
  • Protein enters epithelium by co-transport.
  • Protein moved out epithelium into blood through channel by facilitated diffusion.
• Digestion, Lipid:

  • Triglycerides form large droplets
  • Large droplets are emulsified into small droplets by bile salts. Bile salts are produced in the liver and stored in the gall bladder.
  • Small droplets are hydrolysed into a monoglyceride and 2 fatty acids by lipase. Lipase is made in the pancreas.
  • MG, FA & Bile salts produces, water soluble, micelle.
• Absorption, Lipid:

  • Micelle moves towards membrane.
  • Monoglyceride and fatty acids enter cell by simple diffusion.
  • Triglyceride is reformed in smooth endoplasmic reticulum.
  • Triglycerides combine to create package (chylomicron).
  • Exocytosis into lacteal, package becomes lymph, which eventually enters the blood circulation.