Digestive enzymes

Enzymes help in the breakdown of

food, in a process called chemical
digestion.

Food contains carbohydrates, proteins

and lipids, so a wide range of
enzymes is needed.

• Carbohydrases break down

carbohydrates

• Proteases break down protein
• Lipases break down lipids

Carbohydrate digestion involves two stages:
•First the breakdown of starch to maltose is
catalysed by the enzyme amylase in the mouth and
the lumen of the small intestine.

•Secondly the breakdown of maltose to glucose is
catalysed by the enzyme maltase inside the
mucosa cells of the small intestine.

•Protein digestion in the lumen of the gut starts
with an enzyme called endopeptidase that
catalyses the breakdown of proteins to form
polypeptides.

• An enzyme called an exopeptidase catalyses
the breakdown of polypeptides to produce
dipeptides.

•Inside the cells of the mucosa dipeptidase
enzymes catalyse the breakdown of dipeptides
into amino acids.

Lipid digestion only occurs in the lumen of the
small intestine.
•Lipid digestion cannot start in the stomach
because conditions are too acidic for the lipase
enzymes.

•Bile salts found in bile produced by the liver break
down the fat droplets into smaller droplets.

•This process is called emulsification. It increases
the surface area for the lipase enzymes to work on.

•Lipase from the pancreas catalyses the
breakdown of lipids into fatty acids and glycerol.