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Scientists investigated the effect of regular exercise on skeletal muscle fibres in mice - AQA - A-Level Biology - Question 3 - 2017 - Paper 2
Question 3
Scientists investigated the effect of regular exercise on skeletal muscle fibres in mice. The scientists compared the muscle fibres of mice that had exercised (train... show full transcript
Worked Solution & Example Answer:Scientists investigated the effect of regular exercise on skeletal muscle fibres in mice - AQA - A-Level Biology - Question 3 - 2017 - Paper 2
Step 1
Suggest one reason for the difference in the staining between the muscle fibres of the control mice and the trained mice.
Answer
The trained mice have an increase in aerobic respiration due to regular exercise, leading to more succinic acid dehydrogenase enzyme activity in their muscle fibres.
Step 2
Explain why.
Answer
Trained mice develop more mitochondria and muscle fibres that are adapted for aerobic respiration. This increase allows them to produce more ATP, which enhances their endurance during prolonged exercise, allowing them to sustain activity for a longer time compared to control mice.
Step 3
Using this information, calculate the mean diameter in µm (micrometres) of muscle fibres in this section of tissue.
Answer
First, calculate the radius of the circular area using the given area: Area = πr². Substituting the area: 1.25 = πr² Thus, r = rac{ ext{1.25}}{ ext{π}} o r ext{ (in mm)} o 0.63 ext{ mm}. To find the diameter: Diameter = 2 × r = 2 × 0.63 mm = 1.26 mm = 1260 µm.
Step 4
Describe two differences between these samples of muscle fibres.
Answer
- Young mice exhibit a smaller range of muscle fibre diameters compared to adult mice, indicating more uniformity in size.
- Adult mice display a greater range of muscle fibre diameters, reflecting more variability in muscle fibre types as they age.