Enzymes in digestion

Enzymes are proteins that help the body break down large molecules into smaller ones. They do this by acting as biological catalysts, meaning they speed up chemical reactions without being used up in the process.

Enzymes have a specific shape that fits the molecule they are breaking down, similar to a lock and key. This allows them to efficiently break down large molecules into smaller ones that can be absorbed by the body.

Digestive Enzymes

The three main groups of enzymes are;

  • Carbohydrases
  • Proteases
  • Lipases


Carbohydrase enzymes break down carbohydrates into simple sugars. For example, the carbohydrase amylase breaks down starch into sugar to give us energy. In this case, amylase (the carbohydrase) is the enzyme, which binds to the larger molecule (starch) and breaks it down.

Carbohydrase enzymes are produced in the:

  • Mouth (in saliva), by the salivary glands
  • Pancreas
  • Small intestine


Protease enzymes bind to proteins (long-chain) and break them down into smaller amino acids.

Protease enzymes are produced in the:

  • Stomach
  • Pancreas
  • Small intestine

Stomach acid also plays a role in digesting proteins in the stomach. It is a very strong, highly acidic liquid that helps to break down food and kill harmful microorganisms.


Lipase enzymes bind to lipids (larger molecules) and then break them down into fatty acids and glycerol (smaller molecules).

Lipase enzymes are produced in the:

  • Pancreas
  • Mouth
  • Stomach

Bile is a fluid that is made and released in the liver and is stored in the gallbladder. It helps break down fat into small droplets, which makes it easier for lipase enzymes to break them down for absorption. However, bile is not an enzyme.

Enzyme Conditions and Limits

Different enzymes work well in different conditions:

  • Enzymes in the small intestine work best in alkaline conditions
  • Enzymes in the stomach work best in acidic conditions

The nutrients are absorbed into the blood by the small intestine, which is why all three types of enzymes are produced and work in the small intestine. Even though food does not pass through the pancreas, the pancreas produces enzymes, which are then transported to the organs where they are needed.

Substances that can not be digested

Vitamins, minerals and water do not need to be broken down further as they are small enough. This is why they are not digested.

Unlike other food components, fibre can not be digested by the body. It passes through the digestive system intact and is therefore not absorbed.