5. Digestion

• Define hydrolysis

  The breaking of bonds by addition of h2o
• What is the function of salivary glands

  Secrete saliva - mix of amylase, water and ions
• What is the function of the pancreas

  Pancreatic juice - enzymes in an alkaline solution
• Function of small intestine

  Main area of secretion of enzymes and bile - dueodenum

  Absorption- ileum
• Where does starch digestion begin

  Mouth
• Explain the first step of digestion of starch (mouth)

  Salivary glands release amylase which hydrolyses starch into maltose by breaking glycosidic bonds
• What happens to starch in the stomach

  Salivary amylase is denatured so pancreatic amylase is used to hydrolyse remaining maltose
• What happens to starch on the brush border of small intestines

  Maltase is found and hydrolyses maltose into glucose which is then absorbed
• Which enzymes digest proteins

  Peptidases
• What do endopeptidases hydrolyse

  Peptide bonds in the middle of chain making a larger surface area for exopeptidases
• What do exopeptidases do

  Hydrolyse peptide bonds at the end of the chain producing dipeptides or amino acids
• What digests lipids

  Lipases
• Where does lipid digestion begin

  Duodenum
• What is emulsification

  Bile salts combine with lipid droplets to make them smaller which increases surface area.
• How are lipids then absorbed

  After emulsification lipases hydrolyse them into fatty acids and glycerol which combine with bile salts to form micelles. micelles transport contents to epithelial cells and release into the cell. Where they recombine to form triglycerides and combine with a protein to form chylomicrons
• Why are micelles beneficial for lipid absorption

  They are water soluble so can transport contents to membrane
• What are chylomicrons

  Lipoproteins
• What molecules can be absorbed through the stomach wall

  Water and ethanol
• What is co transport

  When a sodium ion is diffused into the cell with another molecule through a contransport protein.