General digestion

• Endopeptidase - an enzyme which hydrolyses the peptide bonds in the central regions of a polypeptide chain e.g. pepsin and trypsin
• Exopeptidases - an enzyme which hydrolyses the peptide bonds at the terminal ends of a polypeptide chain into dipeptides and amino acids
• By working together the endopeptidase produces more ends for the exopeptidase to work on
• amylase - hydrolyses starch to maltose
• lipase - hydrolyses lipids to fatty acids and glycerol
• maltase - hydrolyses maltose to 2 glucose molecules
• lactase - hydrolyses lactose into glucose and galactose
• sucrase - hydrolyses sucrose to glucose and fructose
• dipeptidase - hydrolyses dipeptides to amino acids
• Intracellular digestion - chemical digestion inside the cells e.g. in the membranes of the epithelial cells in the duodenum
• Extracellular digestion - Chemical digestion outside the cells. e.g. in the lumen of the gut
• Suggest why secreting endopeptidases before exopeptidases increases the rate of protein digestion.

  • the endopeptidase produces more ends for the exopeptidase to hydrolyse
  • this increases the rate of digestion
• Glands:

  • salivary glands secrete saliva
  • oxyntic cells secrete hydrochloric acid
  • chief cells/Zymogen cells secrete pepsinogen
  • Goblet cells secrete mucus
  • pancreas secretes lipase, trypsinogen, exopeptidase and amylase
  • glands secreting enterokinase
  • liver secretes bile
  • Brunner's glands secrete alkaline mucus
• Which areas contain villi?

  Duodenum and ileum
• Sites of mechanical breakdown?

  Mouth and stomach