The functions of enzymes in digestion

The food that we eat contains large complex molecules (polymers) such as starch, fat and protein. However, these large complex molecules can’t be absorbed in the body because they are insoluble. These molecules have to be digested (broken down) into smaller soluble molecules that are easily absorbed by the body.

The breaking down of large insoluble molecules into smaller soluble molecules that are easily absorbed by the body, known as digestion, is facilitated by enzymes. This is just one of the many functions of enzymes that we are going to look at in this article. But first let us look at what an enzyme is.

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What is an enzyme?

An enzyme is a biological substances that facilitates a biological reaction without itself taking part in the reaction.

According to this definition, an enzyme is a biological catalyst.

Role of enzymes in digestion

As I mentioned in the introduction of this article, enzymes play an important role in breaking down the large complex molecules that make up our food into smaller soluble molecules.

Break down of carbohydrates by enzymes in the body

Starch is a soft, white, tasteless insoluble powder, with a chemical formula of (C6H10O5)n. Starch is a type of polymer (known as a polysaccharide) that comprises large numbers of glucose monomers (monosaccharides) joined together.

When you eat food that contains starch the starch cannot be absorbed by the body since it is insoluble. It has to be digested first in order to be absorbed by the body.


The digestion of starch begins with salivary amylase in the mouth. Salivary amylase is produced by the salivary glands in the mouth and pancreatic amylase is produced by the pancreas. Amylase is an enzyme that breaks down starch, primarily into maltose and some glucose.


The maltose produced from the digestion of starch by amylase is then split into two glucose molecules by an enzyme called maltase. The enzyme maltase is released in the small intestine.


Lactase is an enzyme that breaks down lactose, a sugar found in dairy products into glucose and galactose. Lactase is produced in the intestinal tract.


Sucrase is an enzyme secreted by the small intestine. It breaks down sucrose into fructose and glucose. These are simpler sugars that the body can absorb.

Break down of protein by enzymes in the body

Protein is a complex polymer that is made up of smaller molecules called amino acids joined together by a peptide.

Digestion of protein begins in the stomach. When the protein reaches the stomach, hydrochloric acid and enzymes called proteases are released to break down the protein into smaller chains of amino acids. The type of protease that breaks down protein in the stomach is called pepsin.

Pepsin breaks down proteins into smaller peptides and their constituent amino acids.

The pancreas releases more proteases such as trypsin which breaks down the peptides and amino acid chains into individual amino acids. The amino acids are then absorbed in the ileum.


Pepsin is secreted in the stomach to break down proteins into peptides, or smaller chains of amino acids. Those chains of amino acids are broken down further in the small intestine into individual amino acids before being absorbed.


Trypsin is an enzyme secreted by the pancreas but in deactivated form. It is activated in the small intestine. Trypsin then activates additional pancreatic enzymes, such as carboxypeptidase and chymotrypsin, to digest peptides.


Chymotrypsin is an enzyme that breaks down peptides into free amino acids. These free amino acids then absorbed by the walls of the intestines.

Break down of fat by enzymes in the body

Lipase enzymes break down fat into fatty acids and glycerol (a simple alcohol). It is produced in small amounts by your mouth and stomach, and in larger amounts by your pancreas.

Sydney Chako

Mathematics, Chemistry and Physics teacher at Sytech Learning Academy. From Junior Secondary School to Tertiary Level Engineering Mathematics and Engineering Science.


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