Measurements in enzyme-catalysed reactions
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Flip to reveal answersWhat is the independent variable in an enzyme experiment?
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Question
What is the independent variable in an enzyme experiment?
Answer
The **one factor you deliberately change** (e.g. temperature, pH, or substrate concentration).
Question
What is the dependent variable in an enzyme experiment?
Answer
What you **measure** to see the effect — usually the **rate of reaction**.
Question
What is a controlled variable?
Answer
A factor **kept constant** in every run so it does not affect the result and the test stays **fair**.
Question
Name the variables that must be controlled when studying an enzyme.
Answer
**Temperature, pH, substrate concentration, amount of enzyme and time** — each one affects the rate on its own.
Question
Why must other variables be controlled?
Answer
So any change in rate is caused **only** by the factor being tested — this makes the comparison **fair (valid)**.
Question
Give two ways to measure the rate of an enzyme reaction.
Answer
E.g. **volume of gas released**, **colour change of an indicator**, time for a substrate to disappear, or **amount of product** formed.
Question
What does it mean to immobilize an enzyme?
Answer
To **attach or trap** it on a **solid support** (e.g. gel beads) so it stays in one place instead of mixing freely with the substrate.
Question
What is a free enzyme?
Answer
An enzyme **dissolved and mixed freely** in solution with its substrate.
Question
Give three advantages of immobilizing an enzyme.
Answer
It can be **reused** (cheaper), the **product stays pure** (no enzyme contamination), and it is **more stable** over a wider range of conditions.
Question
State one application of immobilized enzymes.
Answer
Immobilized **lactase** is used to make **lactose-free milk** (it breaks lactose into glucose and galactose).
Question
Why is amino acids released a valid measure of protease activity?
Answer
Amino acids are the **product**, so the **more released** per unit time, the **more active** the enzyme — it is proportional to activity.
Question
Why can immobilized enzymes be reused but free enzymes usually can't?
Answer
An immobilized enzyme stays **fixed on its support**, so it can be removed and used again; a free enzyme ends up **mixed into the product** and is lost.
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Topic 3.1 hub
Enzymes and metabolism
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