Digestion

• how is absorption of nutrient by gut epithelial cells possible?

  its only possible if the macromolecules (i.e. carbohydrates, fats and proteins) are first digested into smaller molecules
• how many types of enzymes are needed for the complete digestion of a particular food?

  usually, more than one type is needed
• how are carbohydrates digested?

  • polysaccharides are digested into disaccharides and then monosaccharides
  • amylase hydrolyses starch and glycogen to the disaccharide maltose and maltase digests maltose to the monosaccharide glucose
  • similarly, sucrase digests sucrose and lactase digests lactose
  • the general name for carbohydrate-digesting enzymes is carbohydrase
• how are proteins digested?

  • they are extremely large molecules
  • they are digested into polypeptides, then dipeptides and then amino acids
  • the general names for protein-digesting enzymes are protease and peptidase
  • endopeptidases hydrolyse peptide bonds within the protein molecule, then exopeptidases hydrolyse the terminal or penultimate peptide bonds at the ends of these shorter polypeptides
• how are fats digested?

  they are digested to fatty acids and monoglycerides by one enzyme, lipase
• what is this an image of?

  the digestion of proteins