AQA GCSE Combined Science: Trilogy Biology Paper 1 (Foundation), 2023: Question 2
8 marks · Low Demand difficulty · Short Answer
Identify digestive organs and products, and analyze experimental data on the effect of pH on amylase activity.
Practise this questionQuestion
Question text
02 Enzymes break down food in the digestive system.
Figure 2 shows the human digestive system.
Figure 2
The enzyme amylase digests starch.
02.1 Which part of the digestive system produces amylase?
[1 mark]
Tick ( ) one box.
A B C7
02.2 What molecules are produced when starch is digested?
[1 mark]
Tick ( ) one box.
Amino acids
Fatty acids
Sugars
02.3 Where is digested food absorbed into the blood?
[1 mark]
Tick ( ) one box.
Liver
Pancreas
Small intestine
A student investigated the effect of pH on the digestion of starch by amylase.
This is the method used.
1. Put 1 drop of iodine solution into each well of a spotting tile.
2. Prepare amylase solution at pH 5
3. Mix the amylase solution with starch solution in a test tube.
4. Every 30 seconds remove a drop of the amylase–starch mixture.
Add each drop to iodine solution in a different well of the spotting tile.
5. Record the colour of the iodine solution after the amylase–starch mixture has
been added.
6. Repeat steps 2 to 5 using amylase solutions at different pH values.
02.4 What is the independent variable in this investigation?
[1 mark]
Tick ( ) one box.
pH of the amylase solution
Time when the samples were taken
Volume of iodine solution 10
Figure 3 shows the results on the spotting tile.
Figure 3
02.5 What colours do the symbols in the key represent?
Choose answers from the box.
[2 marks]
black green lilac orange white
02.6 Look at the results for pH 6 in Figure 3.
How many minutes did it take for all the starch to be digested at pH 6?
[1 mark]
minutes
02.7 What was the optimum pH for the amylase to work?
*10* Use Figure 3.
[1 mark]
Tick ( ) one box.
pH 5 pH 6 pH 7 pH 8
Mark scheme
Show the mark scheme
Question 2
AO /
Question Answers Extra information Mark
Spec. Ref.
02.1 C 1 AO1
4.2.1
4.2.2.1
AO /
Spec. Ref.
02.2 sugars 1 AO1
4.2.2.1
AO /
Spec. Ref.
02.3 small intestine 1 AO1
4.2.2.1
AO /
Spec. Ref.
02.4 pH of the amylase solution 1 AO1
4.2.2.1
RPA4
AO /
Spec. Ref.
02.5 black 1 AO2
4.2.2.1
orange 1 RPA3
RPA4
AO /
Spec. Ref.
02.6 3(.0 minutes) allow any value in the range 1 AO3
2.51 to 3.0 (minutes) 4.2.2.1
RPA3
do not accept 2.5 (minutes) RPA4
AO /
Spec. Ref.
02.7 pH 7 1 AO3
4.2.2.1
RPA3
RPA4
Total Question 2 8
How to answer it
Digestion and the Effect of pH on Amylase
What this question tests
This question assesses your ability to identify organs in the digestive system, recall the products of enzyme action, and interpret data from the Required Practical (RPA) investigating how pH affects the rate of starch digestion by amylase.
Anatomy and Enzyme Basics
💡 Key Knowledge
- Amylase is produced in the salivary glands, the pancreas, and the small intestine.
- Starch is a large carbohydrate molecule broken down into sugars (glucose).
- Absorption of small, soluble food molecules occurs in the small intestine.
✅ Correct Answers
- 02.1: C (The small intestine/pancreas area)
- 02.2: Sugars
- 02.3: Small intestine
🧠 Exam Technique: Diagram Labeling
In Figure 2, A is the Liver, B is the Stomach, and C points to the Small Intestine. Even if you aren't sure where the pancreas is, you should know amylase is not made in the liver or stomach, leaving C as the only logical choice.
The pH Investigation
🧠 Identifying Variables
The Independent Variable is the thing you change on purpose to see what happens. In this experiment, the student uses "amylase solutions at different pH values."
Answer 02.4: pH of the amylase solution
❌ Common Errors
Students often confuse the Independent Variable (pH) with the Dependent Variable (the time it takes for starch to disappear). Always ask: "What am I choosing to vary?"
💡 The Iodine Test (02.5)
Iodine solution is used to test for starch. You must know the specific color changes:
- Starch present: Blue-black (or just black)
- Starch absent: Orange-brown (or just orange)
Note: The question provides a list of colors. "Lilac" is for the Biuret protein test, and "Green" is not used for these food tests.
Interpreting the Spotting Tile
🧠 How to read Figure 3
A black circle means starch is still there (digestion is not finished).
A white circle means starch has gone (digestion is complete).
📐 Calculation: Time Taken (02.6)
Look at the row for pH 6:
- At 2.5 minutes, the circle is black (starch still present).
- At 3.0 minutes, the circle is white (starch is gone).
- Therefore, it took 3.0 minutes for all starch to be digested.
Examiner Tip: The mark scheme allows any value between 2.51 and 3.0, but 3.0 is the safest answer based on the data points shown.
✅ Optimum pH (02.7)
The "optimum" is the pH where the enzyme works fastest. This is the row where the circles turn white the earliest.
- pH 5: 5.0+ mins
- pH 6: 3.0 mins
- pH 7: 1.0 min (Fastest!)
- pH 8: 4.5 mins
Answer: pH 7
⚠️ Examiner Commentary
Top-level responses correctly identified that the "optimum" isn't just where the enzyme works, but where it works at the maximum rate. In this practical, that means the shortest time recorded. Many students lose marks by misreading the spotting tile columns—always use a ruler to line up the time with the circles!
Topics
Biology · B2: Organisation
Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Biology Paper 1 (Foundation), 2023. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.