Enzymes are biological catalysts, so factories use them to speed up useful reactions at modest temperatures. Exam questions give you a product, such as juice or washing powder, and ask you to explain what the enzyme does and why the conditions matter.
The underlying ideas are in biological molecules and enzymes. This lesson applies them.
How do you read an industrial enzyme question?
Ask three things:
- Which substrate? What is the enzyme breaking down?
- Which product and why is it useful? What does the change achieve?
- Which condition matters? Temperature, pH or time.
Here are common pairs:
| Enzyme | Substrate | Use |
|---|---|---|
| Protease | Protein stains | Removes food and blood stains in washing powder |
| Lipase | Fats and oils | Removes greasy stains |
| Pectinase | Pectin in fruit cell walls | Gives more juice and clearer juice |
| Amylase | Starch | Makes sugars for syrups and food products |
| Lactase | Lactose | Makes lactose-free milk |
Worked example
The data are invented for practice. A food company tests pectinase on apple pulp. From 100 g of pulp, the juice volume without the enzyme is 45 cm³. With the enzyme, it is 62 cm³, under the same temperature and time.
Question: Calculate the percentage increase in juice and explain why it happens.
Step 1, find the increase. 62 − 45 = 17 cm³.
Step 2, divide by the original. 17 ÷ 45 = 0.3778.
Step 3, convert to a percentage. 0.3778 × 100 = 37.8%, so the increase is about 38% (to 2 significant figures).
Step 4, explain. Pectin holds plant cell walls together and traps juice. Pectinase breaks down pectin, the cell walls break down, and more juice is released.
Step 5, check the fairness. Because temperature, mass of pulp and time were the same in both tests, the extra juice can be linked to the enzyme.
The mistake to watch for
Mistaken answer: “Washing at 90 °C is better because enzymes work faster when hotter.”
Rates do rise with temperature up to the optimum, but above it the enzyme denatures. The active site changes shape, the stain substrate no longer fits, and the enzyme stops working. Washing powder enzymes work at moderate temperatures.
The correction is to say “faster up to the optimum, then denatured”. Always name the shape change when you write “denatured”.
Check yourself
1. A washing powder contains lipase. Which stain does it help to remove, and why?
Show answer
Grease or oil stains. Lipase breaks down fats (its substrate) into smaller molecules that dissolve and wash away.
2. A dairy makes lactose-free milk. Name the enzyme and its substrate.
Show answer
Enzyme: lactase. Substrate: lactose (milk sugar), which it breaks down into simpler sugars.
3. A test gives 30 cm³ of juice without enzyme and 39 cm³ with it. Calculate the percentage increase.
Show answer
39 − 30 = 9. 9 ÷ 30 = 0.3. So the increase is 30%.
Where this leads next
Continue with outlining a genetic-modification concept, where enzymes such as restriction enzymes reappear, then try the biotechnology practice set. The earlier lesson on fermentation shows the microorganism side of the topic.
If your enzyme answers often stop at “it speeds up the reaction”, online one-to-one Biology tuition can train you to finish each explanation with the conditions and the reason. The module overview shows the full route.