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Equilibrate the appropriate enzyme and substrate portions at each selected temperature before starting fresh comparable reactions. Keep pH, mixed enzyme and substrate concentrations, total volume, mixing and measurement method controlled. Use the actual reaction-mixture temperature, not only the bath dial setting.
Video by Professor SNAB. The explanation develops temperature-coefficient measurement. Apply the actual temperature interval and evaluate the rate-comparison assumptions in this lesson.
Viewing focus: Design a controlled enzyme-temperature investigation
After watching, attempt these questions before opening the answers. You can also use the written lesson below.
After watching 1: When does Q10 equal the raw rate ratio directly?
For a 10 °C interval with comparable rates. Other interval sizes require the exponent.
After watching 2: Why can reusing one heated enzyme sample confound the investigation?
Its treatment history can change activity irreversibly. Use fresh or appropriately controlled preparations for the intended comparison.
What you'll be able to do
Equilibrate the appropriate enzyme and substrate portions at each selected temperature before starting fresh comparable reactions. Keep pH, mixed enzyme and substrate concentrations, total volume, mixing and measurement method controlled. Use the actual reaction-mixture temperature, not only the bath dial setting.
Measure an initial rate where possible to reduce depletion and product-accumulation effects. A fixed endpoint can provide a reciprocal-time proxy only when it represents the same small reaction extent in every trial. If the measurement itself is temperature-sensitive, establish that its calibration or threshold remains comparable across conditions.
Q10 describes a rate ratio scaled to a 10 °C increase: Q10 = (r₂/r₁)^[10/(T₂ − T₁)], for suitably comparable positive rates. For an interval of exactly 10 °C, it is simply r₂/r₁. A temperature difference has the same numerical size in Celsius degrees and kelvin, but do not use the absolute-temperature ratio in place of the temperature difference.
A Q10 near two in one range does not establish a universal doubling rule. Above a suitable range, loss of enzyme structure or other system changes can reduce rate. A Q10 below one can describe a decline across that interval, but it does not alone identify the cause. Use the actual data and limits of the measurement model.
Use independent reaction preparations and summarise variability at each temperature. Reusing one heated enzyme preparation across successive treatments can confound temperature with irreversible changes and exposure time. Standardise pre-incubation and timing according to the question being tested.
Probe response, subjective endpoints and small temperature differences can strongly affect a calculated coefficient. Compare justified initial intervals and check whether a simple model is supported over the selected range. A plausible denaturation explanation needs evidence appropriate to the design rather than being assigned to every low reading.
Attempt these problems on paper before opening the worked reasoning. Explain your steps as well as giving a final answer.
Common mistakes to avoid
Key takeaways
Question 1: A separate rate doubles between 20 °C and 35 °C. Calculate Q10.
Q10 ≈ 1.59; the raw ratio two applies to 15 °C, not to 10 °C.
Check the assessed scope and practical or mathematical requirements.
An external explanation or interactive activity to use alongside the lesson. It may include extension material.
Close the notes and answer from memory. Revisit any explanation you cannot yet reconstruct.
Test yourself
Answer a few questions, then review anything you missed.
Start with the quiz above to check the key ideas. You can also choose another topic from the practice library.