A blank nine-step write-up with the correct table headings. Print it for a real lesson and fill it in by hand. See the specimen lab book
Blank write-up: Enzymes
A4. Choose “Save as PDF” as the printer to keep a copy. Page breaks are set when it prints.
Study Hack Lab
RP 5 · Biology
Enzymes
Write-up template
Name
Date
Course
GCSE Biology
Board and specification
AQA GCSE Biology (8461), 4.2.2.1AQA GCSE Combined Science: Trilogy (8464), 4.2.2.1Apparatus and techniques: AT 1, AT 2, AT 5, AT 8
Class and teacher
Aim
Investigate the effect of pH on the rate at which amylase breaks down starch, and find the optimum pH of amylase.
Contents
Plan and risk assessment
Apparatus
Method
Results
Graph
Analysis
Conclusion and evaluation
Make safe and clear up
A blank write-up for use in a real lesson. The headings follow the AQA required practical; the readings are yours to take. Layout v1, practical v2. Original material; not affiliated with AQA, which has not reviewed it.
1 Plan and risk assessment
Amylase is an enzyme that breaks starch down into the sugar maltose. Iodine solution turns blue-black while starch is there and stays orange-brown once it has all gone. Each enzyme works fastest at its optimum pH; away from it the shape of the active site changes, so starch fits less well and the reaction slows.
mean rate of reaction = amount of starch broken down ÷ time taken
Variables
Independent (you change)
Dependent (you measure)
Control (you keep the same)
Prediction
How will the rate at which amylase breaks down starch change from pH 4 to pH 9?
At which of the six buffers will the starch be broken down fastest?
One minute after mixing at pH 4, what colour will a drop turn the iodine?
Risk assessment
Hazard
Harm it could cause
Control
2 Apparatus
Spotting tiles (two for each pH) Hold the drops of iodine solution that each sample is tested in.
Iodine solution in a dropping bottle Turns blue-black when starch is present; stays orange-brown when it is not.
1 % starch solution The substrate.
1 % amylase solution The enzyme.
Buffer solutions: pH 4, 5, 6, 7, 8 and 9 Keep each mixture at one pH: the independent variable.
Three syringes: 5 cm³ for starch, 1 cm³ for buffer, 1 cm³ for amylase (resolution 0.2 cm³ and 0.01 cm³) Measure the same volumes for every run.
Test tubes in a rack Hold the starch with buffer, and the amylase.
Water bath at 37 °C Keeps the temperature the same for every run.
Thermometer (resolution 1 °C) Checks the water bath temperature.
Glass rod Stirs the mixture and carries each drop to a well.
Beaker of water For rinsing the glass rod between drops.
Stopclock (resolution 1 s) Times each run from the moment you mix.
Safety goggles Protect your eyes from iodine solution.
3 Method
Write numbered steps someone else could follow. Say what you measure, with which instrument, and how you keep it a fair test.
4 Results
The table is drawn before you measure. Record each reading to the resolution of the instrument, then work out the mean of your repeats, leaving out any anomaly.
Time for the starch to be broken down · 5 cm³ of 1 % starch (50 mg) with 1 cm³ of buffer, and 1 cm³ of 1 % amylase, at 37 °C. Leave any anomalous time out of the mean.
pH
Time, trial 1 in s
Time, trial 2 in s
Time, trial 3 in s
Mean time in s
Mean rate in mg/min
4
5
6
7
8
9
Anomalies
Ring any anomalous result. Say what probably went wrong and whether you repeated it.
5 Graph
Mean rate of reaction against pH · Choose your axes: the independent variable goes on the x-axis. Label each axis with the quantity and unit.
6 Analysis
Mean rate of reaction
mean rate of reaction = amount of starch broken down ÷ time taken
Answer
The optimum pH
Read the pH below the highest point of your curve.
Answer
7 Conclusion and evaluation
Conclusion
Conclusion: what do your results show? Use your own numbers.
Sources of error
For each, say whether it is systematic or random, and how it affected your results.
Testing a drop only at intervals
Not warming the solutions in the water bath first
Calling the end point at the first drop that looks lighter
Not rinsing the glass rod between drops
Not stirring the amylase into the starch
Judging when the colour has changed
Only six pH values, 1 pH unit apart
Improvement
How could you improve the method? Say why it would help.
8 Make safe and clear up
Rinse the spotting tiles and glass rod under the tap
Pour the mixtures down the sink with plenty of water and rinse the test tubes
Wipe up any iodine on the bench and switch off the water bath
Put the syringes and buffers back on the tray, and wash your hands