Enzymes in digestion

Enzymes are proteins that help the body break down large molecules into smaller ones, acting as biological catalysts. This means 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 maltose.

Carbohydrase enzymes are produced in the:

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


Protease enzymes bind to long-chain proteins 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. This highly acidic liquid helps break down food and kills harmful microorganisms.


Lipase enzymes bind to larger lipid molecules and break them down into smaller fatty acids and glycerol.

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.

It’s important to note that bile itself is not an enzyme.

Enzyme Conditions and Limits

Different enzymes function optimally under different conditions:

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

Nutrients are absorbed into the bloodstream by the small intestine, which is why it produces all three types of enzymes. Although food doesn’t pass through the pancreas, this organ still produces enzymes that are transported to where they are needed.

Substances that cannot be digested

Vitamins, minerals and water do not need to be broken down further as they are already small enough, which 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.

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