Metabolism is the sum of all the chemical reactions in the cells of the body - AQA - GCSE Biology - Question 2 - 2018 - Paper 1

• Males have a higher metabolic rate than females after five years of age.
• The mean metabolic rate of females decreases faster than males up to 25 years of age.

To calculate the decrease in metabolic rate:

1. The mean metabolic rate for males at 5 years is 53 kJ/m/hour.

2. The mean metabolic rate for males at 45 years is 36 kJ/m/hour.

3. The decrease in metabolic rate is:

   $$53 - 36 = 17 \ kJ/m/hour$$

4. Using the formula:

   $$percentage \ decrease = \left( \frac{17}{53} \right) \times 100 = 32.1 \%$$

Thus, the percentage decrease is 32.1.

1. Person R's heart rate increased more gradually than Person S's heart rate, which showed a larger initial rise.

2. After 5 minutes of exercise, Person R's heart rate plateaued at 99 bpm, while Person S's heart rate continued to rise, reaching 132 bpm.

To complete the graph for Person S:

• The x-axis should be labeled with 'Time in minutes' ranging from 0 to 5 minutes.
• The heart rate points for Person S should be plotted at the corresponding times showing an increasing trend.

Person S's heart rate is 132 bpm after 5 minutes of exercise. If the resting heart rate is 100 bpm, the delta is:

With a decrease of 12 beats per minute:

So, it would take approximately 2.7 minutes for the heart rate to return to its resting state.

To test the hypothesis, conduct the following steps:

• Recruit a balanced sample of smokers and non-smokers of similar age and fitness levels.
• Ensure all participants have the same health status and are matched for activity level.
• Have participants perform the same exercise intensity for a set duration while measuring their heart rates before, during, and after exercise.
• Control variables: time of day, type of exercise, and environment.
• Analyze the heart rate data for both groups to determine differences in response to exercise.