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Auralith Learning

Year 8 · Science · Nutrition and digestion · Lesson 3

Enzymes and digestion

What enzymes are, the lock and key model, the three digestive enzymes and their products, and how temperature and pH affect enzymes.

Whiteboard video lesson: Enzymes and digestion

23-minute video lesson

Teaching, worked examples and 20 practice questions solved step by step.

Watch free for a month

What your child will learn

  • Explain what an enzyme is
  • Describe the lock and key model
  • Name amylase, protease and lipase and their products
  • Explain how temperature and pH affect enzymes
  • Interpret results from enzyme experiments

The method

  1. Enzymes are biological catalysts: they speed up reactions without being used up.
  2. The substrate fits the enzyme's active site (lock and key); enzymes are specific.
  3. Amylase: starch to sugars. Protease: protein to amino acids. Lipase: lipids to fatty acids and glycerol.
  4. Enzymes work best at 37 °C; too hot and they are denatured.

Key words: enzyme, catalyst, active site, substrate, amylase, protease, lipase, denatured, optimum.

Worked examples

The first three practice questions from the lesson, with every step.

Question 1

What does amylase break down, and what does it make?

  1. Step 1: Amylase: starch
  2. Step 2: starch → sugars (glucose)

Answer: Starch into sugars (glucose)

Question 2

What does lipase break down, and what does it make?

  1. Step 1: Lipase: lipids (fats)
  2. Step 2: lipids (fats) → fatty acids and glycerol

Answer: Lipids (fats) into fatty acids and glycerol

Question 3

Name the enzyme that digests protein.

  1. Step 1: Protein → protease

Answer: Protease