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Science lesson plan · 9th grade (Year 10 in England) · 30 minutes

How enzymes work: active sites, temperature and pH

Cells, genetics and evolution

CCSS NGSS.HS-LS1-6England: GCSE Combined Science: Organisation (enzymes)

Objective and success criteria

Students will: How enzymes work: active sites, temperature and pH.

  • I can answer questions on today's skill on my own, without help.
  • I can explain each step and say why it works.
  • I can check my answer and spot a mistake.

Before and after

Needs first: Digestive enzymes and the molecules they make

Leads to: Work out enzyme reaction rates from experimental data

Materials: Microscope images or slides, Cell diagrams, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).

Warm-up · 4 min

  • Quick retrieval from earlier learning (Digestive enzymes and the molecules they make). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. Which enzyme is described here: breaks starch down into sugars? (amylase (a carbohydrase) / protease / lipase) → amylase (a carbohydrase)Prompt: The enzyme's name often sounds like the food it breaks down.
  2. Amylase was mixed with starch at different temperatures. Iodine was used to time how long the starch took to disappear: 20 °C: 8 min 30 °C: 4 min 40 °C: 8 min 50 °C: 9 min 60 °C: starch still present after 20 min At which temperature did amylase work fastest, in °C? → 30 °CPrompt: Fastest means the shortest time.
  3. Which organ makes bile? (gall bladder / pancreas / stomach / liver) → liverPrompt: Bile is stored in one organ but made in another.

Hook · 3 min

  • Show a microscope image of cells and ask what students think they are looking at.
  • Share the objective: How enzymes work: active sites, temperature and pH. Read the success criteria together.

I do: model it · 7 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: Why does a reaction speed up as temperature rises towards the optimum?
  • Step 1: More kinetic energy means more successful collisions between enzyme and substrate.
  • Step 2: So the answer is: Molecules move faster, so enzyme and substrate collide more often
  • Answer: Molecules move faster, so enzyme and substrate collide more often
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 6 min

  • Do these together. Students try each step on whiteboards before you reveal it.
  • Use the hints as prompts rather than giving the answer.
  1. Why does a reaction speed up as temperature rises towards the optimum? (The substrate becomes an enzyme / The active site disappears / The enzyme gets bigger / Molecules move faster, so enzyme and substrate collide more often) → Molecules move faster, so enzyme and substrate collide more oftenPrompt: Think about kinetic energy.
  2. Enzymes: which statement is NOT true? (Enzymes are biological catalysts. / Enzymes are living things. / Most human enzymes work best at about 37 °C. / Enzymes are proteins.) → Enzymes are living things.Prompt: Is the effect of cold permanent?

You do: independent practice · 7 min

  • Students work on the student sheet. Circulate and check the first two answers of every student early.
  • Students who finish: write a question of their own for a partner, with the answer.

The 6 questions are on the student sheet below, with answers in the key.

Exit ticket · 3 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. Pepsin works best at pH 2. Where in the body does it work? (the blood / the small intestine / the mouth / the stomach) → the stomachPrompt: Which part of the gut is very acidic?
  2. Enzymes: which statement is NOT true? (Enzymes are not used up in the reactions they speed up. / Most human enzymes work best at about 37 °C. / All enzymes work best at pH 7. / Enzymes are biological catalysts.) → All enzymes work best at pH 7.Prompt: Is the effect of cold permanent?

Watch out for

  • Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
  • Remembering facts without the reason: ask "why?" and "what is the evidence?"

Support and stretch

Support

  • Review first: Digestive enzymes and the molecules they make.
  • Use concrete materials: microscope images or slides.
  • Give the first step of each question, or a partly worked example to finish.
  • Pair with a confident partner for the guided practice.

Stretch

  • Move on to: Work out enzyme reaction rates from experimental data.
  • Explain a common mistake in writing and how to fix it.
  • Write a word problem that uses today's skill, then solve a partner's.

Homework and more practice

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-9.

Free lesson plan from eurekami.com/lesson-plan-builder

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How enzymes work: active sites, temperature and pH

Name

Date

Score/ 6

  1. Question 1

    A human enzyme has an optimum temperature of about 37 °C. What is the enzyme most likely to be doing at 65 °C?

    • A. working slowly, but not denatured
    • B. working at or near its fastest rate
    • C. denatured and no longer working

  2. Question 2

    Enzymes: which statement is NOT true?

    • A. Enzymes are biological catalysts.
    • B. Enzymes are proteins.
    • C. All enzymes work best at pH 7.
    • D. Most human enzymes work best at about 37 °C.

  3. Question 3

    Why can an enzyme only act on one type of substrate?

    • A. Enzymes are too big
    • B. Other substrates are dead
    • C. Enzymes are used up after one reaction
    • D. Only that substrate fits the shape of its active site

  4. Question 4

    A human enzyme has an optimum temperature of about 37 °C. What is the enzyme most likely to be doing at 38 °C?

    • A. working slowly, but not denatured
    • B. working at or near its fastest rate
    • C. denatured and no longer working

  5. Question 5

    Pepsin works best at pH 2. Where in the body does it work?

    • A. the mouth
    • B. the stomach
    • C. the small intestine
    • D. the blood

  6. Question 6

    A human enzyme has an optimum temperature of about 37 °C. What is the enzyme most likely to be doing at 15 °C?

    • A. working slowly, but not denatured
    • B. working at or near its fastest rate
    • C. denatured and no longer working

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Answer key: How enzymes work: active sites, temperature and pH

  1. 1. C. denatured and no longer working

  2. 2. C. All enzymes work best at pH 7.

  3. 3. D. Only that substrate fits the shape of its active site

  4. 4. B. working at or near its fastest rate

  5. 5. B. the stomach

  6. 6. A. working slowly, but not denatured