Plan a controlled temperature investigation with amylase
Compare starch breakdown while holding other enzyme conditions constant.
Mapped to the named 0654 section using teaching from the corresponding single-science course. A 0654-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade.
Before you begin
- Recall protein building blocks and the distinction between a molecule and a living cell.
- Use the supplied observations, quantities and units rather than assuming an optimum for every enzyme.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What is the intended independent variable in this investigation?
What you will learn
- Compare starch breakdown while holding other enzyme conditions constant.
- Apply the explanation to the stated evidence and recognise the limits of the model.
Define the test and measurement
A supervised amylase investigation can compare breakdown of a fixed starch amount at different temperatures. Prepare comparable enzyme and starch portions and allow them to reach the assigned water-bath temperature before starting the reaction. Use a consistent mixing step and start the timer when enzyme and substrate are combined.
At regular specified intervals, transfer a small reaction sample to a separate iodine drop on a tile. Blue-black indicates starch detected; the first sample that leaves iodine yellow-brown marks the defined detection endpoint. Iodine belongs in the sampled test, not in the main reaction vessel.
Control and evaluate
Vary temperature while matching pH, enzyme and starch volumes and concentrations, total reaction volume, mixing and sampling intervals. Use clean sampling equipment and working iodine comparisons, and repeat trials at each temperature. A no-active-enzyme comparison helps evaluate non-enzymatic change.
Record actual reaction temperature and endpoint times. The first negative sample indicates starch below the test’s detection level, not proof that every molecule has vanished or that all products are glucose. Practical work requires teacher-approved preparations, eye protection and supervision; written plans do not establish laboratory competence.
Sources for this lesson
Pause and explain
Why use separate iodine drops for sampled reaction mixture?
Worked example
A student changes both temperature and amylase concentration between trials. Can the activity difference be attributed to temperature alone?
Show the worked solution
- Identify the intended independent variable: temperature.
- Enzyme concentration changes too.
- Either difference can alter measured activity.
Answer No; enzyme concentration is a confounder and should be matched for a temperature comparison.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
State the independent variable and one suitable dependent measurement.
Give me a hint
Name the changed condition and the measured endpoint.
Compare my reasoning
- Change water-bath temperature.
- Measure time to the first starch-negative sampled test.
Temperature; time to the specified iodine endpoint.
Look for these in your work
- Distinguish the two variables.
- Define the endpoint.
Name four conditions to match between temperature trials.
Give me a hint
Keep enzyme, substrate and other assay conditions comparable.
Compare my reasoning
- Match enzyme volume and concentration.
- Match starch volume and concentration.
- Keep pH and sampling interval the same.
Match enzyme and starch quantities/concentrations, pH and sampling interval; also match total volume and mixing.
Look for these in your work
- Name at least four relevant controls.
- Do not control away the intended temperature change.
At a high temperature, no starch-negative sample is obtained before the 300 s stopping time. How should this be recorded?
Give me a hint
Do not invent a completion time.
Compare my reasoning
- The specified endpoint was not observed.
- Its time is greater than the observation window or unknown.
- More than 300 s is not the same as exactly 300 s.
Record endpoint not reached within 300 s, rather than a completed 300 s endpoint.
Look for these in your work
- Preserve the censored observation.
- Do not claim a measured completion time.
Common mistakes
- Do not add iodine to the entire reaction mixture.
- Do not equate the first starch-negative sample with measured glucose production.
What can you explain now?
Why use separate iodine drops for sampled reaction mixture?
Compare with the explanation
To detect starch in samples without mixing iodine into the main reaction.
Keep the measurement method separate.
After trying it yourself, choose your next review. This is your self-assessment.
Your review choice appears on Today. Sign in to sync it across devices.
Make it stick
Plan the temperature experiment using variables, sampling, endpoint, repeats and supervision.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.