Science lesson plan · 9th grade (Year 10 in England) · 60 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 · 6 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.
- 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.
- 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: 7 min 50 °C: 8 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.
- Which organ makes bile? (gall bladder / liver / pancreas / stomach) → liverPrompt: Bile is stored in one organ but made in another.
Hook · 6 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 · 12 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 · 12 min
- Do these together. Students try each step on whiteboards before you reveal it.
- Use the hints as prompts rather than giving the answer.
- Why can an enzyme only act on one type of substrate? (Other substrates are dead / Enzymes are too big / Enzymes are used up after one reaction / Only that substrate fits the shape of its active site) → Only that substrate fits the shape of its active sitePrompt: Think of a lock and its key.
- Enzymes: which statement is NOT true? (All enzymes work best at pH 7. / Enzymes are not used up in the reactions they speed up. / Enzymes are biological catalysts. / Most human enzymes work best at about 37 °C.) → All enzymes work best at pH 7.Prompt: Is the effect of cold permanent?
You do: independent practice · 17 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 8 questions are on the student sheet below, with answers in the key.
Exit ticket · 7 min
- Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
- Why does a reaction speed up as temperature rises towards the optimum? (The active site disappears / The enzyme gets bigger / Molecules move faster, so enzyme and substrate collide more often / The substrate becomes an enzyme) → Molecules move faster, so enzyme and substrate collide more oftenPrompt: Think about kinetic energy.
- Enzymes: which statement is NOT true? (Cold temperatures denature enzymes permanently. / Most human enzymes work best at about 37 °C. / Enzymes are not used up in the reactions they speed up. / Enzymes are proteins.) → Cold temperatures denature enzymes permanently.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