Digestion

• Amylase is produced in the pancreas and salivary glands
• Maltase is produced in the small intenstine
• Endopeptidases and exopeptidases are more efficient than exopeptidases on their own because endopeptidases break bonds in the middle of the chain. This creates a larger surface area for enzyme action
• Digestion is the hydrolysis of large insoluble molecules into small soluble molecules that can be absorbed across cell membranes
• Bile is produced in the liver
• Bile is stored in the gall bladder
• Bile is released via the bile duct
• Bile emulsifies fats to increase surface area for lipase action and it neutralises the digestive juices in the small intestine
• Enzymes are substrate specific, meaning different enzymes digest and breakdown different biological molecules
• Digestive enzymes are extracellular enzymes, meaning they work outside of cells
• The digestion of carbohydrates takes place in the mouth and small intestine
• The four enzymes involved in the digestion of carbohydrates are:

  • amylase
  • maltase
  • sucrase
  • lactase
• Maltase, sucrase and lactase are membrane bound disaccharidases
• Maltase breaks down maltose into glucose
• Sucrase breaks down sucrose into glucose and fructose
• Lactase breaks down lactose into glucose and galactose
• Amylase hydrolyses the polysaccharide starch to the disaccharide maltose by hydrolysing the glycosidic bonds
• Maltase us produced in the cell surface membrane of the epithelial cells of the small intestine
• The lining of the small intestine is folded and there are microvilli present to increase the surface area and allow more membrane-bound disaccharidases to fit
• The digestion of proteins takes places in the stomach and the small intestine
• Endopeptidases hydrolyse peptide bonds in the stomach and small intestine
• Exopeptidases hydrolyse peptide bonds in the small intestine
• Dipeptidases hydrolyse peptide bonds in the cell-surface membrane of the small intestine
• Endopeptidases and exopeptidases are produced in the pancreas but dipeptidases are produced in the small intestine
• In the stomach, solid lipids are turned into a fatty liquid consisting of fat droplets (but this is not digestion)
• Bile salts bind to fatty liquid and break the fat droplets into smaller ones via emulsification
• The digestion of lipids only takes place in the small intestine by lipase
• Lipase is produced in the pancreas
• Lipases hydrolyse the ester bond in triglycerides to form fatty acids and glycerol (and monoglycerides in incomplete hydrolysation)
• Amylase is produced in the salivary glands and pancreas and is secreted in the mouth and small intestine
• The stomach has a pH of 1 to kill pathogens and because it is the specific protease's optimum pH
• ingestion happens in the mouth and egestion happens from the anus
• Peristalsis occurs throughout the digestive tract