AQA GCSE Combined Science: Trilogy Biology Paper 1 (Foundation), June 2025: Question 4
13 marks · Standard Demand difficulty · Short Answer
Analyze heart rate and lactic acid data during and after exercise to calculate percentage increase and evaluate fitness.
Practise this questionQuestion
Question text
04 This question is about exercise.
04.1 Which two substances do muscles need during exercise?
[2 marks]
Tick ( ) two boxes.
Carbon dioxide
Glucose
Lactic acid
Oxygen
Urea 22
Two people exercised on running machines.
The two people ran at the same speed.
Each person’s heart rate was monitored:
• before exercising
• while exercising
• after they stopped exercising.
Figure 8 shows the results.
Figure 8
04.2 How many minutes did person B exercise for?
[2 marks]
23Number of minutes =
04.3 Calculate the percentage increase in heart rate for person B during the exercise.
*22Use the equation:*
maximum heart rate – resting heart rate
percentage increase = × 100
resting heart rate
Give your answer to 2 significant figures.
[3 marks]
Percentage increase (2 significant figures) = %
04.4 A student stated:
‘Person B is fitter than person A.’
Give two pieces of evidence to support the student’s statement.
Use Figure 8.
[2 marks]
Immediately after exercise, the concentration of lactic acid in the blood of the two
people was measured.
Table 5 shows the results.
Table 5
Concentration of lactic acid
in arbitrary units
Person A 22
Person B 4
04.5 Complete the bar chart in Figure 9.
You should:
• use a suitable scale for the y-axis
• plot the data from Table 5
• label each bar.
[3 marks]
Figure 9
04.6 The concentration of lactic acid in the blood of person A is proportional to the intensity
of the exercise.
Which symbol means ‘proportional to’?
[1 mark]
Tick ( ) one box.
~
>
∝
Mark scheme
Show the mark scheme
AO /
Question Answers Extra information Mark
Spec. Ref.
04.1 glucose 1 AO2
4.4.2.1
4.4.2.2
oxygen 1
AO /
Spec. Ref.
04.2 40 – 15 1 AO3
25 (minutes) 1 AO2
4.4.2.2
AO /
Spec. Ref.
04.3 allow a correct calculation given AO2
to 2 significant figures using 4.4.2.2
person A for 2 marks
104 – 60 allow 44 1
× 100 × 100
60 60
73.3(3333333…) 1
73 (%) 1
allow 2 marks for
102 - 60
× 100 = 70 (%)
allow 1 mark for 0.73
AO /
Spec. Ref.
04.4 answers must be comparative
allow converse if clearly
referring to person A
any two from: 2 AO3
person B 4.4.2.2
• has a lower resting heart rate
• has a smaller increase in
heart rate
• has a lower maximum heart
rate
• reaches their maximum heart allow takes longer to reach their
rate later maximum heart rate
• has a shorter recovery time allow takes a shorter time to
reach resting heart rate
allow has a lower oxygen debt
if no other marks awarded allow
1 mark for person B has lower
heart rate
AO /
Spec. Ref.
04.5 suitable scale for y-axis a bar height must use at least 1 AO2
half of graph paper 4.4.2.2
bars plotted correctly allow a tolerance of ± small 1
square
the bars can be in any order
ignore the width of the bar
ignore if bars are touching
bars labelled correctly allow the use of a correct key 1
AO /
Spec. Ref.
04.6 ∝ 1 AO1
4.4.2.2
Total Question 4 13
Question 5
How to answer it
Exercise, Heart Rate Response & Lactic Acid
What this question tests
This question evaluates your foundational knowledge of human biology during physical activity and your core mathematical and graphing skills in AQA GCSE Combined Science: Trilogy:
- Cellular Respiration: Identifying reactants required by contracting muscle cells.
- Graph Interpretation: Reading baseline, peak, and recovery times on a rate–time graph.
- Percentage Increase Calculations: Accurately substituting graph data into a formula and rounding to significant figures.
- Data Evaluation: Comparing physiological indicators (heart rate, recovery, lactic acid) to assess physical fitness.
- Graph Construction: Selecting a linear scale, plotting discrete categories accurately, and adding clear labels.
- Mathematical Symbols: Identifying the direct proportionality symbol.
Substances Needed by Muscles During Exercise
Identifying reactants for cellular respiration
✅ Correct Answer
- Glucose [1 mark]
- Oxygen [1 mark]
💡 Key Knowledge
During exercise, muscle cells contract much more frequently and need more energy. They get this by transferring energy via aerobic respiration:
glucose + oxygen → carbon dioxide + water (+ energy)
Therefore, muscle tissues require an increased supply of glucose and oxygen.
❌ Common Errors
- Ticking carbon dioxide or lactic acid — these are products, not reactants supplied to muscles.
- Ticking urea — this is a metabolic waste product produced by the liver from excess amino acids.
🧠 Exam Technique
Carefully read the prompt: "substances do muscles need". That tells you to select what enters the cells (reactants/nutrients), not the waste products formed after exercise.
Duration of Exercise for Person B
Extracting time intervals from a line graph
✅ Correct Answer
25 minutes [2 marks]
• 1 mark for identifying the correct interval: 40 - 15
• 1 mark for the final answer: 25
🧠 How to Read Figure 8
- Start of exercise: The heart rate of Person B remains flat at 60 bpm until 15 minutes, where it begins rising sharply.
- End of exercise: Heart rate remains at peak plateau (104 bpm) until 40 minutes, where it immediately starts dropping.
- Calculation: End time (40 min) − Start time (15 min) = 25 minutes.
❌ Common Errors
- Writing 40 minutes: reading only when exercise ended rather than the total duration.
- Assuming exercise started at 0 minutes: ignoring the initial 15-minute resting baseline.
Percentage Increase in Heart Rate for Person B
Data extraction, substitution, and significant figures
📐 Step-by-Step Calculation
• Resting heart rate (before 15 min) = 60 bpm
• Maximum heart rate (peak plateau between 26–40 min) = 104 bpm (allow 102 bpm)
percentage increase = ((104 - 60) / 60) × 100 = (44 / 60) × 100
44 / 60 × 100 = 73.3333...%
The first two significant digits are 7 and 3. The following digit is 3 (less than 5), so round down:
73%
✅ Final Mark Scheme Summary
- Correct substitution: (104 - 60) / 60 × 100 [1 mark]
- Calculated value: 73.3...% [1 mark]
- Final answer to 2 s.f.: 73% [1 mark]
❌ Common Calculation Traps
- Dividing by the wrong number: Dividing by the maximum heart rate (104) instead of the resting heart rate (60).
- Forgetting significant figures: Leaving the answer as 73.3% or 73.33% loses the final accuracy mark!
- Omitting the subtraction: Calculating (104 / 60) × 100 = 173% without subtracting resting heart rate.
Evidence that Person B is Fitter than Person A
Comparative analysis of graph features
✅ Correct Evidence Points (Any Two) [2 marks]
Answers must be strictly comparative (state "lower/faster/shorter" or compare B to A):
- Person B has a lower resting heart rate (60 bpm vs 86 bpm).
- Person B has a lower maximum heart rate during exercise (104 bpm vs 136 bpm).
- Person B has a smaller increase in heart rate (44 bpm vs 50 bpm).
- Person B takes longer to reach their maximum heart rate / reaches max later.
- Person B has a shorter recovery time / returns to resting heart rate faster (takes 10 min vs 16+ min).
💡 Biological Reason
A fitter person has a stronger heart muscle with a larger stroke volume (more blood pumped per beat). Therefore, their heart does not need to beat as many times per minute to supply muscles with sufficient oxygen and glucose, and they pay off their oxygen debt faster.
🧠 Exam Technique: Always Use Comparatives
- Saying "Person B's heart rate is low" will lose marks because it is an absolute statement.
- You must say: "Person B has a lower resting heart rate than Person A".
Completing the Bar Chart (Figure 9)
Presenting discrete biological data accurately
✅ Mark Scheme Criteria
- Suitable scale on y-axis [1 mark]: Linear, numbered at regular intervals, with bars occupying at least half the vertical height of the grid (e.g. 0 to 24 with major gridlines every 2 or 4 units, or 0 to 25 with 5 units per major line).
- Bars plotted correctly [1 mark]: Height of Person A = 22, Height of Person B = 4 (within ±½ a small square tolerance).
- Bars labelled correctly [1 mark]: Clear labels below the bars for "Person A" and "Person B" (or a matching labeled key).
🧠 Examiner Guidelines for Full Marks
- Scale Choice: Count the vertical squares. Ensure 22 fits easily while filling more than 50% of the grid height. Do not create irregular steps (e.g., 0, 5, 10, 15, 20, 22). Keep the spacing uniform!
- Bar Widths: Bars can be any width and may touch or have gaps, but keep both bars equal width for neatness.
- Ruler: Always use a sharp pencil and ruler for straight horizontal bar tops.
❌ Common Errors
- Non-linear scale: Writing the table numbers (4 and 22) directly on the y-axis notches instead of setting up an even numerical scale.
- Squashed graph: Choosing a scale where the tallest bar (22) occupies less than half the vertical height of the grid.
- Missing labels: Plotting the bars correctly but forgetting to write "Person A" and "Person B" underneath.
Symbol for 'Proportional to'
Mathematical symbols in science
✅ Correct Answer
Tick the third box: ∝ [1 mark]
💡 Meaning of the Symbols
- ~ means approximately or order of magnitude.
- > means greater than.
- ∝ means directly proportional to (e.g. lactic acid ∝ exercise intensity).
Topics
Biology · B4: Bioenergetics
Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Biology Paper 1 (Foundation), June 2025. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.