Back to GCSE Biology Revision Home

Digestive Enzymes

GCSEAQABiology FoundationBiology HigherCombined Science FoundationCombined Science Higher

Digestive Enzymes Revision

Digestive Enzymes

Enzymes are particularly important in the human digestive system. They break down large food molecules, like carbohydrates, proteins and lipids, into smaller ones so they can be absorbed into the blood and transported around the body.

Purpose of Digestive Enzymes

Food is made up of big molecules such as starch, proteins and fats. They are too big to pass through the walls of the small intestine and be absorbed into the blood, therefore, we must digest them first. This is done by digestive enzymes such as carbohydrases, proteases and lipases.

The body needs to be able to absorb nutrients from food so they can be used to make new carbohydrates, proteins and lipids.

Glucose is a product of carbohydrate digestion and is used to produce energy in aerobic respiration.

GCSECombined Science FoundationCombined Science HigherBiology FoundationBiology HigherAQA

Carbohydrases

Carbohydrases are digestive enzymes that break down carbohydrates into simple sugars.

Starch is a common carbohydrate in the human diet. It is made up of glucose molecules joined together.

Amylase is a carbohydrase that breaks down starch into maltose (comprised of two glucose molecules). 

Amylase digests starch in the mouth and small intestine. It is produced in the salivary glands, pancreas and small intestine.

GCSECombined Science FoundationCombined Science HigherBiology FoundationBiology HigherAQA

Proteases

Proteases are digestive enzymes that break down proteins into amino acids

Proteins are digested in the stomach by pepsin and in the small intestine by other proteases.

Proteases are produced in the stomach, pancreas and small intestine.

GCSECombined Science FoundationCombined Science HigherBiology FoundationBiology HigherAQA

Bile and Lipases

The digestion of lipids (fats) is a 2 step process. First they get emulsified by bile, then they get broken down by lipases.

Bile is produced by the liver, stored in the gall bladder and then released into the small intestine. It has 2 uses:

  • It is an alkaline substance so neutralises hydrochloric acid from the stomach. This creates better conditions for enzymes in the small intestine so they can digest food efficiently.
  • Bile also emulsifies fats which means it breaks them into small droplets. This gives them a greater surface area for lipases to work on, making digestion faster.

Lipases are digestive enzymes that break down lipid molecules into glycerol and fatty acids, in the small intestine. They are made in the pancreas and small intestine.

GCSECombined Science FoundationCombined Science HigherBiology FoundationBiology HigherAQA

Digestive Enzymes Example Questions

Amylase breaks down starch into maltose.

MME Premium Laptop

Save your answers with

MME Premium

Gold Standard Education

The stomach, pancreas and small intestine.

MME Premium Laptop

Save your answers with

MME Premium

Gold Standard Education

Bile neutralises stomach acid and emulsifies fats.

MME Premium Laptop

Save your answers with

MME Premium

Gold Standard Education

Digestive Enzymes Worksheet and Example Questions

Site Logo

Enzymes Questions

GCSEOfficial MME
MME Premium UI
Product

MME Premium Membership

£19.99

/month

Learn an entire GCSE course for maths, English and science on the most comprehensive online learning platform. With revision explainer videos & notes, practice questions, topic tests and full mock exams for each topic on every course, it’s easy to Learn and Revise with the MME Learning Portal.

Sign Up Now