Figure 8 shows the heart rate of person A and person B. Person A does not do any regular exercise. Person B has been running regularly for one year. (a) Both people rested for the first 6 minutes, then did the same high intensity exercise for the next 12 minutes, then rested. Compare the heart rates of person A with the heart rates of person B. (4) (b) The stroke volume for person B before exercising was 61 ml per beat. Calculate the cardiac output for person B before exercising. Give your answer in litres per minute. (3) (c) The cardiac output for person A during exercise was 5.5 litres per minute. Explain why the heart rate for person A needed to be higher than the heart rate for person B during exercise. (3)

GCSE Edexcel Biology Combined Science Respiration: Figure 8 shows the heart rate of

Figure 8 shows the heart rate of person A and person B - Edexcel - GCSE Biology Combined Science - Question 5 - 2020 - Paper 1

Question 5

Figure 8 shows the heart rate of person A and person B. Person A does not do any regular exercise. Person B has been running regularly for one year. (a) Both people... show full transcript

Worked Solution & Example Answer:Figure 8 shows the heart rate of person A and person B - Edexcel - GCSE Biology Combined Science - Question 5 - 2020 - Paper 1

Step 1

Compare the heart rates of person A with the heart rates of person B.

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Answer

During the initial 6 minutes of rest, both person A and person B maintain similar heart rates. However, once high-intensity exercise begins, the heart rate of person A increases significantly more than that of person B, indicating a greater cardiovascular strain for person A. After the exercise, person B’s heart rate returns to baseline more quickly than person A’s, suggesting better cardiovascular fitness due to regular exercise.

Step 2

Calculate the cardiac output for person B before exercising.

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Answer

Cardiac output (CO) can be calculated using the formula: $CO = Stroke\, Volume imes Heart\, Rate$ Assuming the heart rate before exercise for person B is around 75 bpm (for the sake of this calculation), the cardiac output would be: $CO = 61 \, ml/beat \times 75 \, beats/min = 4575 \, ml/min = 4.575 \, litres/min$

Step 3

Explain why the heart rate for person A needed to be higher than the heart rate for person B during exercise.

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Answer

Person A's heart rate needed to be higher than that of person B during exercise in order to achieve an adequate cardiac output to meet the increased metabolic demands of the body. Since person A does not engage in regular exercise and has a lower cardiovascular efficiency, their heart rate must increase more significantly to supply sufficient oxygen and nutrients to the muscles compared to person B, who is more physically conditioned and requires less effort to maintain the same output.

Figure 8 shows the heart rate of person A and person B - Edexcel - GCSE Biology Combined Science - Question 5 - 2020 - Paper 1

Worked Solution & Example Answer:Figure 8 shows the heart rate of person A and person B - Edexcel - GCSE Biology Combined Science - Question 5 - 2020 - Paper 1

Compare the heart rates of person A with the heart rates of person B.

Calculate the cardiac output for person B before exercising.

Explain why the heart rate for person A needed to be higher than the heart rate for person B during exercise.

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