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

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

To find the percentage decrease:

1. Original metabolic rate (at 15 years) = 43 kJ/h

2. New metabolic rate (at 25 years) = 39 kJ/h

3. Decrease = 43 - 39 = 4 kJ/h

4. Percentage decrease:

   $$\frac{4}{43} \times 100 = 9.30\%$$

   After rounding to 3 significant figures, the percentage decrease is 9.30%.

1. Person R's heart rate rose to 99 beats per minute after 5 minutes, while Person S's heart rate reached 132 beats per minute, indicating a higher response to exercise stamina.
2. Person R's heart rate increased more gradually from 60 to 99 beats per minute, whereas Person S's heart rate rose more sharply from 100 to 132 beats per minute.

1. The x-axis should be labeled with the time in minutes, ranging from 0 to 5.
2. The scale could be increments of 1 minute, showing each heart rate plotted accurately according to the data.

1. Person S's heart rate at rest is 100 beats per minute.
2. The final heart rate after 5 minutes of exercise is 132 bpm.
3. Heart rate decrease of 12 beats per minute will happen after exercise.
4. Time to return to resting heart rate = (132 - 100) / 12 = 2.67 minutes, or approximately 2.67 minutes.

1. Select two groups of participants: smokers and non-smokers, with at least five individuals in each group.
2. Ensure both groups are matched for age, gender, and pre-exercise fitness levels.
3. All participants will perform the same exercise at a set intensity for a specific duration.
4. Measure the heart rate of each participant before and immediately after exercise.
5. Record the heart rates and analyze the difference in increase between the two groups, controlling for other variables such as health status and baseline fitness.