digestion & absorption

• enzymes used to break down carbohydrates:

  amylase

  membrane bound disaccharidases
• amylase

  produced in salivary glands & pancreas

  • hydrolysis of glycosidic bonds polysaccharides → disaccharides
• membrane bound disaccharidases

  found in the membrane of epithelial cells in the ileum

  • hydrolysis of glycosidic bonds disaccharides → monosaccharides
• enzymes used to break down proteins

  endopeptidases

  exopeptidases

  membrane bound dipeptidases
• endopeptidases

  hydrolyses peptide bonds in the centre of the chain
• exopeptidases

  hydrolyses peptide bonds at the ends of the chain
• membrane bound dipeptidases

  hydrolyses peptide bonds between 2 amino acids
• enzymes breaking down lipids

  lipase - produced in the pancreas
• lipase

  hydrolyses ester bonds in triglycerides
• bile salts

  produced in the liver, stored in the gallbladder

  • emulsifies lipids to form micelles
• how are glucose and amino acids absorbed?

  co-transport:

  • sodium ions actively transport: epithelial cells → blood
  • sodium ions facilitated diffuse from the ileum to the epithelial cells using a cotransporter protein
  • amino acids and glucose can attach and transports as well to the epithelial cells
  • then transports into the blood
• describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels.

  1. Micelles contain bile salts and fatty acids
  2. release fatty acids to cell lining of the ileum
  3. Fatty acids absorbed by diffusion;
  4. Triglycerides formed ; endoplasmic reticulum
  5. Vesicles move to cell membrane; via exocytosis and goes into a lymph vessel
• Describe the role of micelles in the absorption of fats into the cells lining the ileum. 

  1. Micelles include bile salts and fatty acids;
  2. Make the fatty acids soluble in water;
  3. release fatty acids to cell lining of the ileum
  4. Maintain high concentration of fatty acids
  5. Fatty acids absorbed by diffusion;