S4.1.5 For the adult
Enzymes
Starch on a plate hardly changes in days. In your gut it breaks down in minutes. What speeds it up?
What this chapter teaches
Enzymes are proteins that speed up reactions and are not used up. The substrate fits the active site like a key in a lock. Activity rises with temperature to an optimum and then falls fast, because the enzyme is denatured. Each enzyme has an optimum pH.
Three questions to ask
There is no one right wording. Listen for the idea.
- Why is an enzyme not used up in a reaction?
- Why does a reaction slow right down at 60 °C, and does the enzyme recover when it cools?
- Why does an enzyme that suits the stomach not work well in the mouth?
After the chapter, the learner can
- Explain how enzymes speed up reactions using the lock and key model
- Explain how temperature and pH change enzyme activity
What they copy into their notebook
Enzyme: a protein that speeds up a reaction and is not used up. The substrate fits the active site. Warmer is faster up to the optimum, about 37 °C. Past it the enzyme is denatured. Each has an optimum pH.