A-Level AQA Biology 6.3 Skeletal Muscles (A Level only): Scientists investigated the effe

Scientists investigated the effect of regular exercise on skeletal muscle fibres in mice - AQA - A-Level Biology - Question 3 - 2017 - Paper 1

Question 3

Scientists investigated the effect of regular exercise on skeletal muscle fibres in mice. The scientists compared the muscle fibres of mice after six weeks of regula... 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 1

Step 1

Succinic acid dehydrogenase is an enzyme used in the Krebs cycle. Suggest one reason for the difference in the staining between the muscle fibres of the control mice and the trained mice.

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Answer

The trained mice likely have a higher concentration of succinic acid dehydrogenase due to enhanced aerobic respiration resulting from regular exercise. This leads to more intense staining compared to the control mice.

Step 2

The scientists then compared the length of time that the control mice and the trained mice could carry out prolonged exercise. The trained mice were able to exercise for a longer time period than control mice. Explain why.

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Answer

Trained mice can sustain prolonged exercise due to increased muscle efficiency. Regular exercise enhances aerobic respiration, resulting in greater ATP production. This allows trained mice to perform longer periods of activity without fatigue, as they rely less on anaerobic processes that lead to lactate accumulation.

Step 3

Using this information, calculate the mean diameter in µm (micrometres) of muscle fibres in this section of tissue.

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First, calculate the effective diameter of the field of view by determining the area per fibre. If the area of one field is 1.25 mm² for 15 fibres, the total area per fibre is:

$\text{Area per fibre} = \frac{1.25 \text{ mm}^2}{15} \approx 0.0833 \text{ mm}^2$

Assuming that the muscle fibres are circular, the area of a circle is given by:

$A = \pi r^2$

To find the radius, we rearrange that to find:

$r = \sqrt{\frac{A}{\pi}}$

Substituting the area per fibre into the equation yields:

$r = \sqrt{\frac{0.0833}{\pi}} \approx 0.1625 \text{ mm}$

To find the diameter in micrometres, we use:

$d = 2r = 2 \times 0.1625 \text{ mm} = 0.325 \text{ mm} = 325 \text{ µm}$

Step 4

Describe two differences between these samples of muscle fibres.

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Answer

The muscle fibres from young mice tend to exhibit larger diameters compared to those from adult mice, indicating a difference in muscle development.
Young mice muscle fibres may show a greater range of variation in diameter than those from adult mice, suggesting that muscle fibre maturation stabilizes size.

Step 5

Describe two differences between these samples of muscle fibres.

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Answer

The distribution of muscle fibre diameters in young mice is typically wider, with some fibres significantly larger than those in adult mice, indicating developmental growth stages.
Adult mice muscle fibres may exhibit more uniformity in diameter compared to young mice, reflecting a more consistent and mature muscle structure.

Scientists investigated the effect of regular exercise on skeletal muscle fibres in mice - AQA - A-Level Biology - Question 3 - 2017 - Paper 1

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 1

Succinic acid dehydrogenase is an enzyme used in the Krebs cycle. Suggest one reason for the difference in the staining between the muscle fibres of the control mice and the trained mice.

The scientists then compared the length of time that the control mice and the trained mice could carry out prolonged exercise. The trained mice were able to exercise for a longer time period than control mice. Explain why.

Using this information, calculate the mean diameter in µm (micrometres) of muscle fibres in this section of tissue.

Describe two differences between these samples of muscle fibres.

Describe two differences between these samples of muscle fibres.

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