AQA GCSE Biology Biology Paper 1 (Foundation), June 2024: Question 4

14 marks · Low Demand difficulty · Extended Answer

Describe food tests for starch and sugar, and interpret experimental data on the breakdown of starch in different breads by salivary amylase.

Practise this question

Question

Question text

04 Starch and sugar are two types of carbohydrate.

04.1 Describe the chemical tests that a student could use to show if bread contains:

• starch

• sugar.

You should include the results of a positive test and a negative test for each type

of carbohydrate.

[4 marks]

A student investigated three types of bread.

For each type of bread, the student:

• put a square piece of bread into their mouth

• did not chew the bread

• recorded the time taken for the bread to taste sweet.

Table 2 shows the results.

Table 2

Time taken for bread to

Type of bread

taste sweet in seconds

Brown 43

*15* White 35

Wholemeal 57

04.2 Complete the sentences.

Choose answers from the box.

[2 marks]

amylase fat lipase protease sugar

The starch in the bread was broken down by the

enzyme .

The enzyme broke down the starch into17 .

04.3 What was the independent variable in the investigation?

[1 mark]

Tick ( ) one box.

The size of the piece of bread

The temperature of the mouth

The type of bread

04.4 Give two conclusions that can be made from the results in Table 2.

[2 marks]

Table 2 is repeated below.

Table 2

Time taken for bread to

Type of bread

taste sweet in seconds

Brown 43

White 35

Wholemeal 57

The student improved the investigation.

Table 3 shows the results.

Table 3

Time taken for bread to

taste sweet in seconds

Type of bread

Test 1 Test 2 Test 3 Mean

*17* Brown 38 43 45 42

White 35 31 39 35

Wholemeal 58 55 61 X

04.5 What did the student do to improve the investigation?

Use Table 2 and Table 3.

[2 marks]

04.6 Calculate value X in Table 3.

[2 marks]

X = seconds

04.7 Why should the student do the investigation with more people?

[1 mark]

Tick ( ) one box.

Each person’s sense of taste is different.

More people would make the investigation safer.

There are many different types of bread.

Mark scheme

Show the mark scheme

Question 4

AO /

Question Answers Mark

Spec Ref.

04.1 Level 2: Scientifically relevant facts, events or processes are 3–4 AO1

identified and given in detail to form an accurate account. 4.2.2.1

RPA4

Level 1: Facts, events or processes are identified and simply 1–2

stated but their relevance is not clear.

No relevant content 0

Indicative content:

Starch

• iodine (solution) tests for starch

• iodine (solution) turns to blue-black or black or dark blue (if

starch is present)

• iodine (solution) remains unchanged / yellow / orange / brown (if

no starch is present)

Sugar

• Benedict’s (reagent / solution) tests for sugar

• boil or heat (to at least 60 °C)

• Benedict’s (reagent / solution) turns green / yellow / orange /

brown / (brick) red (if sugar is present)

• Benedict’s (reagent / solution) remains unchanged / blue (if no

sugar is present)

For Level 2, the response must give details of the tests for starch

and sugar.

AO /

Question Answers Extra information Mark

Spec Ref.

04.2 must be in this order AO1

amylase 1 4.2.2.1

sugar 1

AO /

Spec Ref.

04.3 the type of bread MARK SCHEME – – 1 – AO2

4.2.2.1

AO /

Spec Ref.

04.4 allow answers in terms of rate, AO3

such as fastest / slowest to taste 4.2.2.1 13

sweet

allow to break down for to taste

sweet, throughout

any two from: 2

• white bread tastes sweet in

the least time

• wholemeal bread takes most

time to taste sweet

• brown bread takes more time

than white bread to taste

sweet

allow a correct comparison of

time to taste sweet for two types

of bread, for 1 mark

allow any two correct

comparisons of time to taste

sweet for two types of bread, for

2 marks

ignore use of figures, unqualified

AO /

Spec Ref.

04.5 repeated (each type of bread) 1 AO3

4.2.2.1

calculated a mean 1

AO /

Spec Ref.

04.6 58 + 55 + 61 174 1 AO2

allow 4.2.2.1

58 (seconds) allow student’s total correctly 1

divided by 3

if no answer given in answer

MARKspaceSCHEMEallow answer– written in – –

Table 3

AO /

Spec Ref.

04.7 each person’s sense of taste is 1 AO3

14 different 4.2.2.1

Total Question 4 14

How to answer it

Carbohydrate Digestion & Food Tests

WHAT THIS QUESTION TESTS

This question assesses core practical knowledge and working scientifically skills from Topic 2: Organisation:

Required Practical 4 (Food Tests): Identifying reagents, experimental conditions, and colour changes for starch (iodine) and sugars (Benedict's).
Enzyme Action: Identifying that salivary amylase catalyses the breakdown of insoluble starch into soluble sugars.
Working Scientifically: Identifying independent variables, drawing comparative conclusions from experimental tables, understanding how repeats increase reliability, and calculating the arithmetic mean.

PART 04.1 • 4 MARKS

Chemical Tests for Starch and Sugar

Describing procedures and positive/negative outcomes

✅ Model Answer (Level 2: 4 Marks)

Test for Starch: Add iodine solution to the bread.
- Positive result: Solution changes from brown/orange to blue-black.
- Negative result: Solution remains orange / brown / yellow.
Test for Sugar: Add Benedict's reagent to the bread and heat in a water bath (to at least 60 °C).
- Positive result: Solution turns green / yellow / orange / brick-red.
- Negative result: Solution remains blue.

🧠 Exam Technique: Level of Response

Level 2 (3–4 marks): You must describe the tests for both starch and sugar, including both positive and negative results.
Level 1 (1–2 marks): Identifying only one test correctly or giving incomplete colour changes.
Crucial Step: Always state that Benedict's solution must be heated / boiled. Omitting heat will cap your practical description!

❌ Common Errors

Confusing the reagents: Writing "Biuret" (tests for proteins) or "Ethanol / Sudan III" (tests for lipids).
Leaving out negative results: The prompt explicitly states: "include the results of a positive test and a negative test". Failing to mention negative results costs easy marks.
Vague colour changes: Writing "turns dark" instead of blue-black, or "turns warm" instead of brick-red.

Mark Scheme: Level 2 (3–4 marks) requires details of reagents, positive colour, negative colour, and the heating step for sugar across both food types.

PART 04.2 • 2 MARKS

Enzyme Breakdown of Starch

Completing the sentences using the provided word bank

✅ Correct Answer

The starch in the bread was broken down by the enzyme amylase .

The enzyme broke down the starch into sugar .

💡 Key Knowledge

Amylase is a carbohydrase enzyme produced in the salivary glands and pancreas.
It breaks down large, insoluble starch molecules into smaller, sweet-tasting soluble sugars (such as maltose and glucose).
This is why plain bread starts to taste sweet if held in the mouth without chewing.

Mark Scheme: 1 mark for amylase ; 1 mark for sugar . Must be in this exact order.

PART 04.3 • 1 MARK

Identifying the Independent Variable

Understanding experimental design

✅ Correct Selection

[ ] The size of the piece of bread
[ ] The temperature of the mouth
[ ✓ ] The type of bread

🧠 Exam Technique

Independent Variable: The factor deliberately changed by the scientist (here, Brown vs White vs Wholemeal).
Dependent Variable: The factor being measured (time taken to taste sweet).
Control Variables: Factors kept constant to ensure a fair test (e.g. piece size, not chewing).

Mark Scheme: 1 mark for ticking "The type of bread".

PART 04.4 • 2 MARKS

Conclusions from Experimental Data

Analysing Table 2 (Time taken to taste sweet: White = 35 s, Brown = 43 s, Wholemeal = 57 s)

✅ Correct Conclusions (Any Two)

Conclusion 1: White bread takes the least time to taste sweet (or breaks down the fastest).
Conclusion 2: Wholemeal bread takes the most time to taste sweet (or breaks down the slowest).
Alternative: Brown bread breaks down faster than wholemeal / slower than white bread.

❌ Common Errors

Simply copying figures: Writing "White was 35 and brown was 43" is just repeating raw data, not stating a conclusion.
Missing the comparative link: Failing to use comparative words like fastest, slowest, least time, or more time than.

Mark Scheme: 1 mark for each valid comparison/conclusion (max 2 marks). Ignore unqualified figures.

PART 04.5 • 2 MARKS

Improving Investigation Quality

Comparing Table 2 (single test) to Table 3 (three tests + mean)

✅ Correct Answer

Repeated the test (conducted 3 trials for each bread type).
Calculated a mean (average).

💡 Why is this an improvement?

Repeating tests and calculating a mean reduces the effect of random errors and allows anomalous results to be identified and excluded, improving the reliability of the data.

Mark Scheme: 1 mark for repeated / repeats; 1 mark for calculated a mean.

PART 04.6 • 2 MARKS

Calculation: Finding the Mean Value (X)

Working out the mean time for Wholemeal bread

📐 Step-by-Step Calculation

From Table 3 for Wholemeal bread: Test 1 = 58 s, Test 2 = 55 s, Test 3 = 61 s

Step 1: Sum the individual trials
Total = 58 + 55 + 61 = 174
Step 2: Divide by the number of trials (3)
Mean = 174 ÷ 3 = 58

Value X = 58 seconds

❌ Calculation Traps

Input errors on calculators: Typing 58 + 55 + 61 ÷ 3 gives 133.3 because the calculator divides only 61 by 3! Always press equals (=) before dividing, or use brackets.

Mark Scheme: 1 mark for showing working: (58 + 55 + 61) / 3 or 174 / 3; 1 mark for correct answer of 58.

PART 04.7 • 1 MARK

Evaluating Human Subjectivity

Why test with more people?

✅ Correct Selection

[ ✓ ] Each person's sense of taste is different.
[ ] More people would make the investigation safer.
[ ] There are many different types of bread.

🧠 Exam Technique

Taste is a subjective measurement (based on human sensation). Different people have different sensitivities to sweetness and produce saliva containing different concentrations of amylase. Testing multiple people helps minimise individual variation.

Mark Scheme: 1 mark for ticking "Each person's sense of taste is different."

Topics

Biology · Required Practicals · B2: Organisation · Required Practicals

Question and mark scheme from the AQA GCSE Biology examination, Biology Paper 1 (Foundation), June 2024. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.