AQA GCSE Biology Biology Paper 1 (Foundation), November 2021: Question 4
9 marks · Low Demand difficulty · Short Answer
Identify features of carbohydrates and investigate the effect of temperature on the rate of reaction of amylase breakdown of starch.
Practise this questionQuestion
Question text
04 Carbohydrates are needed as part of a balanced diet.
04.1 Which formula shows glucose?
[1 mark]
Tick ( ) one box.
C6H12O6
CO2
H2O
O2
04.2 Which type of enzyme breaks down starch?
[1 mark]
Tick ( ) one box.
Carbohydrase
Lipase
Protease 16
A student investigated the effect of temperature on the activity of the
enzyme amylase.
Figure 7 shows the apparatus used.
Figure 7
This is the method used.
1. Set up the apparatus as shown in Figure 7.
2. After 5 minutes, pour the starch solution into the amylase solution and mix.
3. Remove one drop of the amylase-starch solution mixture and place onto a
spotting tile.
4. Immediately add two drops of iodine solution to the amylase-starch solution mixture
on the spotting tile.
5. Record the colour of the iodine solution added to the amylase-starch solution
mixture.
6. Repeat steps 3 to 5 every minute until the iodine solution is yellow-brown.
04.3 Name apparatus Q in Figure 7.
[1 mark]
04.4 Why were the starch solution and the amylase solution left for five minutes before
mixing them together?
[1 mark]
Tick ( ) one box.
*16* So that both solutions could reach 10 °C
So that the student could calculate a mean
So that the student could repeat the investigation
So that the student had time to draw a table of results18
Figure 8 shows the results.
Figure 8
04.5 How many minutes did it take until the iodine solution and amylase-starch solution
mixture was yellow-brown?
Use Figure 8.
[1 mark]
minutes
04.6 How could a more accurate time be obtained?
[1 mark]
Tick ( ) one box.
Add more iodine solution to the spotting tile.
Test the mixture with iodine solution every 30 seconds.
Test the mixture with iodine solution for more time.
Use two drops of amylase-starch solution mixture in each test.19
The student repeated the investigation at five different temperatures.
Table 2 shows the results.
Table 2
Time taken until iodine solution and mixture
Temperature in °C
was yellow-brown in minutes
20 5
35 2
50 7
65 12
80 Remained blue-black
04.7 Which temperature did the enzyme work quickest at?
[1 mark]
Tick ( ) one box.
20 °C
35 °C
50 °C
65 °C
04.8 Explain why the iodine solution remained blue-black in the investigation at 80 °C.
[2 marks]
Mark scheme
Show the mark scheme
AO /
Question Answers Extra information Mark
Spec. Ref.
04.1 C6H12O6 1 AO1
4.4.1.1
4.4.2.1
04.2 carbohydrase 1 AO1
4.2.2.1
04.3 beaker allow water bath 1 AO1
4.2.2.1
RPA5
04.4 so that both solutions could 1 AO2
reach 10 °C 4.2.2.1
RPA5
04.5 10 / ten (minutes) 1 AO3
4.2.2.1
RPA5
04.6 test the mixture with iodine 1 AO3
solution every 30 seconds 4.2.2.1
RPA5
04.7 35 °C 1 AO3
4.2.2.1
RPA5
04.8 enzyme / amylase is denatured allow active site / enzyme has 1 AO2
or changed shape 4.2.2.1
enzyme / amylase stops working do not accept enzyme / RPA5
amylase has died
(so) starch is not broken down 1
or
starch is still present
Total 9
How to answer it
Enzymes: Investigating the Effect of Temperature on Amylase Activity
This 9-mark question assesses core practical knowledge from AQA Required Practical 5 (Enzymes) and topic 4.2 (Organisation):
- Recalling the chemical formula of glucose and classes of digestive enzymes.
- Identifying standard laboratory apparatus and practical controls (equilibration time).
- Interpreting visual experimental data from spotting tiles and numerical table data.
- Suggesting improvements to increase accuracy (shorter sampling intervals).
- Explaining the mechanism of enzyme denaturation at high temperatures using biological terminology.
Basic Recall: Carbohydrates and Digestive Enzymes
✅ Correct Selections
04.1 Formula for glucose:
C₆H₁₂O₆ [1 mark]
04.2 Enzyme that breaks down starch:
Carbohydrase [1 mark]
💡 Key Knowledge
- Glucose is a simple hexose sugar with 6 Carbons, 12 Hydrogens, and 6 Oxygens: C₆H₁₂O₆ .
- Starch is a complex carbohydrate. The general enzyme group breaking it down is carbohydrase (specifically, amylase).
- Protease breaks proteins into amino acids; lipase breaks lipids into glycerol and fatty acids.
Experimental Setup & Equilibration (Figure 7)
✅ Correct Answers
04.3 Name apparatus Q:
Beaker (or water bath) [1 mark]
04.4 Why leave solutions for 5 minutes?
So that both solutions could reach 10 °C [1 mark]
🧠 Exam Technique: Temperature Equilibration
When investigating temperature, reagents must be at the intended test temperature before the reaction begins.
Leaving the tubes in the water bath allows heat exchange to occur so both reach thermal equilibrium (10 °C). If mixed immediately at room temperature, the initial reaction rate would not represent 10 °C.
Interpreting Results & Improving Accuracy (Figure 8)
✅ Correct Answers
04.5 Time taken until yellow-brown:
10 (or ten) minutes [1 mark]
04.6 How to obtain a more accurate time:
Test the mixture with iodine solution every 30 seconds. [1 mark]
📐 Step-by-Step Reading (Figure 8)
- Row 1: 4 wells = 0, 1, 2, 3 minutes (all blue-black).
- Row 2: 4 wells = 4, 5, 6, 7 minutes (all blue-black).
- Row 3: 8 min (blue-black), 9 min (blue-black), 10 min (yellow-brown), 11 min (yellow-brown).
- First well showing yellow-brown is at index 10 minutes.
💡 Accuracy vs Repeatability
Testing every 30 seconds decreases the measurement interval, narrowing down the exact moment all starch is fully digested (giving a closer value to the true time).
Temperature Effects & Denaturation (Table 2)
✅ Correct Answers
04.7 Quickest temperature:
35 °C [1 mark]
04.8 Why iodine remained blue-black at 80 °C [2 marks]:
- The enzyme / amylase is denatured (or active site has changed shape / enzyme stopped working) [1 mark]
- Therefore, starch is not broken down (or starch is still present) [1 mark]
🧠 Exam Technique: "Quickest" vs Time
Remember: Rate = 1 / time.
The enzyme works quickest when the time taken is the lowest (2 minutes at 35 °C). Do not confuse longest time with fastest rate!
❌ Common Errors to Avoid
- Never say enzymes "die" or are "killed": Enzymes are protein molecules, not living organisms! The mark scheme explicitly states: do NOT accept enzyme has died. Always say denatured.
- Forgetting the second mark: Stating only that the enzyme denatures gets 1/2. You must link it back to the observation: "so starch is not digested / starch remains".
- Confusing the colour change: Iodine is yellow-brown; it turns blue-black in the presence of starch.
• 1 mark: enzyme / amylase is denatured OR active site / enzyme has changed shape OR enzyme stops working.
• 1 mark: (so) starch is not broken down OR starch is still present.
Topics
Biology · Required Practicals · B2: Organisation · B4: Bioenergetics · Required Practicals
Question and mark scheme from the AQA GCSE Biology examination, Biology Paper 1 (Foundation), November 2021. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.