Digestive enzymes

Digestion is the breakdown of large, insoluble food molecules into small, water-soluble molecules using mechanical and chemical processes. Mechanical digestion includes:

  • chewing in the mouth
  • churning in the stomach

Chemical digestion involves enzymes. These are proteins that function as biological catalysts.

Different enzymes

Enzymes can break down nutrients into small, soluble molecules that can be absorbed. For example, amylase causes the breakdown of starch into simple sugars.

Where enzymes are produced

EnzymeSubstrateEnd-productsWhere produced
Salivary amylaseStarchMaltoseSalivary glands
ProteaseProteinAmino acidsStomach, pancreas
LipaseLipids (fats and oils)Fatty acids and glycerolPancreas
Pancreatic amylaseStarchMaltosePancreas
MaltaseMaltoseGlucoseSmall intestine

Where digestion happens

  • Proteases catalyse the breakdown of proteins into amino acids in the stomach and small intestine
  • Lipases catalyse the breakdown of fats and oils into fatty acids and glycerol in the small intestine
  • Amylase catalyses the breakdown of starch into maltose in the mouth and small intestine
  • Maltase catalyses the breakdown of maltose into glucose in the small intestine