Rates of enzyme-controlled reactions — OCR GCSE Biology
Test yourself on Rates of enzyme-controlled reactions with OCR GCSE practice questions.
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Rates of enzyme-controlled reactions explained
Investigating how temperature alters enzyme activity requires precise thermal control across a spectrum of temperatures, typically from 10 to 60 °C.
Read the full explanation
Thermostatically controlled electric water baths or beakers of water heated by Bunsen burners on wire gauze provide controlled reaction environments. To ensure valid comparisons, enzyme and substrate solutions must be placed into separate boiling tubes and pre-equilibrated in the water bath for at least 5 minutes before mixing, verifying that the reaction commences precisely at the set incubation temperature. Digital thermometers monitor thermal stability. Safety protocols include wearing eye protection, securing hot glassware with tongs, and preventing boiling water splash injuries.
Your focus
- Set up water baths across multiple target temperatures safely and monitor thermal stability with thermometers.
- Demonstrate the necessity of pre-equilibrating enzyme and substrate separately prior to initiating kinetic assays.
- Explain how precise temperature control prevents premature thermal denaturation and preserves experimental validity.
Rates of enzyme-controlled reactions exam tips
Marking Points
- Set up and regulate water baths across a range of temperatures (e.g. 10 to 60 °C) using thermostatically controlled heaters or Bunsen burners.
- Pre-equilibrate enzyme and substrate in separate tubes in the water bath before mixing so the reaction starts at the target temperature.
- Monitor and record water bath temperature continuously using a calibrated digital thermometer to ensure stability within ±0.5 °C.
- Wear eye protection, use heat-resistant gloves or tongs for hot tubes, and keep Bunsen burners on safety flame when not in active heating.
Examiner Tips
- 💡In questions asking how to ensure a reaction occurred at the intended temperature, state: 'pre-incubate enzyme and substrate separately in the water bath'.
- 💡Mention using an electric thermostatically controlled water bath rather than a Bunsen burner to improve temperature stability.
Common Mistakes
- Mixing enzyme and substrate before placing them in the water bath, meaning the reaction proceeds during temperature adjustment.
- Assuming water bath dials are accurate without independently measuring the actual liquid temperature with a thermometer.
- Allowing water bath temperatures to drift significantly during kinetic measurement runs, invalidating the independent variable.