Digestion and Absorbtion

• Digestion

  Breaking food down into smaller pieces that can be absorbed into the bloodstream.
• Molecules digested


  • Carbohydrates
  • Lipids
  • Proteins
• Amylases


  Starch broken down by Amylase breaks glycosidic bond forming maltose.

  • Produced in the pancreas and saliva glands
  • Digest carbohydrates in the mouth, stomach and small intestine
• Disaccharidases


  Membrane-bound enzymes that hydrolyze disaccharides into monosaccharides

  • Sucrose hydrolyzed by Sucrase into Glucose and Fructose
  • Lactose hydrolyzed by Lactase into Galactase and Glucose
  • Maltose hydrolyzed by Maltase into Glucose
• Disaccharidases


  • Sucrase
  • Lactase
• Protein digestion


  1. Endopeptidases hydrolyze peptide bonds within the protein, only works in acidy conditions, released in stomach

  2. Exopeptidases hydrolyze peptide bonds at the ends of the protein,

  3. Dipeptidases hydrolyze the peptide bond between two amino acids
• Lipase


  Enzyme produced in the pancreas that hydrolyzes the ester bonds, and catalyzes the break down of lipids into monoglycerides and fatty acids.
• Lipid digestion


  1. Bile salts emulsify lipids into small droplets, increasing surface area for lipase

  2. Lipase hydrolyzes triglycerides into fatty acids and monoglycerides

  3. Fatty acids and monoglycerides stick to bile salts to form micelles.
• Micelles


  • Spherical structures containing fatty acids, monoglycerides and bile salts
  • Deliver fatty acids and monoglycerides to epithelial cells in the ileum
• Absorption of Lipids

  1. Micelles contact the epithelial cells lining the ileum.

  2. Micelles break down releasing fatty acids and monoglycerides (they are non-polar) and diffuse across cell surface membrane to epithelial cell

  3. Then transported to endoplasmic rectillium, where they recombine to make triglycerides

  4. In ER and Golgi Apparatus they are combines with cholesterol to form chylomicrons

  5. Chylomicrons move out of cell by exocytosis to capillaries
• Villi and microvilli in the ileum increase surface area for rapid absorption