Lesson 9 of 9

Helpful bacteria

Goal: Describe the role of bacteria in the gut.

Puzzles for this lesson

Word search0 of 7 foundCrossword0 of 42 letters
An illustration of one bacterium

Trillions of bacteria live in your gut, mostly in the large intestine. Most of them help you.

  • They help to break down food. Gut bacteria feed on food that your own enzymes cannot digest, such as fibre.
  • They make vitamins. Some gut bacteria make vitamin K, which your body absorbs and uses.
  • They keep harmful microorganisms out. They take up the space and the food, so harmful ones find it hard to grow.
Wholemeal bread, cereal, chickpeas, a pear and celery
Food for bacteria. You cannot digest fibre, but your gut bacteria can break some of it down.

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Key words in this lesson

Vitamins Needed in small amounts, and named with letters such as A, C and D

Enzyme A substance that speeds up the chemical reactions of digestion

Large intestine Where water is absorbed and faeces are formed

Gut bacteria Microorganisms that live in the intestine and help to break down food

For teachers: AQA 3.8.4