Topic Five (1.5): Bacteria and enzymes in digestion

Topics Icon.png Objectives

By the end of this topic you should be able to:

  • describe the role of enzymes in digestion;

  • describe the role of bacteria in digestion.

Introduction Icon.png Introduction

In this topic you will learn how digestion (the breakdown of large (insoluble) molecules into small (soluble) molecules so that they can pass into the bloodstream) relies on bacteria and enzymes. Enzymes are very important in Biology as well as being really useful and amazing.


Interact Icon.png Working through your coursebook

VIEW - Resource 1: Food for Thought PowerPoint (slides 14-18) Download VIEW - Resource 1: Food for Thought PowerPoint (slides 14-18)

  • Read pages 12–13. Not all bacteria are bad! Make sure that you know the importance of bacteria in the intestines and understand what the word ‘probiotic’ means.

WATCH - Bacteria in digestion | Physiology | Biology | FuseSchool (YouTube)

  • Enzymes speed up digestion. Remember that carbohydrase breaks starch into sugar (keep a piece of bread in your mouth for long enough and it begins to taste sweet), protease breaks down protein into amino acids and lipase breaks down lipids/fats into fatty acids and glycerol.
  • If you like you can make a model digestive system by following the Gross Science project below. Be careful not to make too much mess! (Scroll down the page - past the video)

COMPLETE - The Ultimate Gross Science Project (hubpages.com) Links to an external site.


Review Icon.png Review

Answer summary questions 1 and 2 on page 13.


Bridge Icon.png Support activity for this topic

COMPLETE - B2 1.5 Animation: Digestion and enzymes (Kerboodle) Links to an external site.


Stretch Icon.png Extension activity for this topic

Learn about how digestion works:

WATCH - The Stomach (Twig) [Not available on sample course]

Enzymes are amazing, find out how they power the reactions in our body:

WATCH - Enzymes (Twig) [Not available on sample course]


Download Icon.png Check your answers

Student Book Answers - Biology 2 Chapter 1 Download Student Book Answers - Biology 2 Chapter 1