This required practical covers Required Practical: Effect of Temperature on Respiration Rate within Respiration for GCSE Biology. Topic 2: Respiration It is section 8 of 17 in this topic. Revise both the method and the reason for each step, because practical questions often test understanding rather than pure recall.
🧪 Required Practical: Effect of Temperature on Respiration Rate
Method
- Add yeast suspension and glucose solution to a boiling tube
- Place the tube in a water bath set to a specific temperature (e.g. 20°C)
- Attach a delivery tube leading to a test tube of limewater (or use a gas syringe to collect CO₂)
- Start a timer and count the number of CO₂ bubbles produced in 5 minutes (or measure volume of gas collected)
- Repeat at different temperatures (e.g. 20°C, 30°C, 40°C, 50°C, 60°C)
- Repeat each temperature 3 times and calculate a mean
Key Variables
- Independent variable: Temperature of the water bath
- Dependent variable: Volume of CO₂ produced (or number of bubbles per minute)
- Control variables: Volume and concentration of glucose solution, amount of yeast, time measured
Expected Results
Rate of respiration increases as temperature rises (more kinetic energy → more enzyme-substrate collisions). Above the optimum (~40°C), rate drops sharply as enzymes denature. At 60°C, little or no CO₂ is produced.
Common Exam Errors
- Saying enzymes "die" at high temperatures — enzymes are not alive, they denature
- Forgetting to mention that repeats are needed to calculate a reliable mean
- Not identifying the control variables when asked
Practice questions for Respiration
Where in the cell does aerobic respiration take place?
Give three uses of energy released from respiration.
Quick recall flashcards
Is respiration endothermic or exothermic?
Exothermic — it releases energy from glucose.
This energy is used for movement, growth, and keeping warm.
Word equation for aerobic respiration?
glucose + oxygen → carbon dioxide + water
(+ energy released)