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Quiz yourself on RespirationGet your flashcardsBuild my revision planTrack my progress🧪 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
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