# Explain how the ultrastructure of a skeletal muscle cell (myocyte) is adapted for its function.

> IB DP Biology Higher Level (2023 syllabus) — B2.3 Cell specialisation · Explain · 4 marks

## Mark scheme (4 marks)

1. Abundant mitochondria provide ATP for muscle contraction via aerobic respiration
2. Extensive sarcoplasmic reticulum stores and releases calcium ions to trigger contraction
3. Multiple peripheral nuclei allow a large cytoplasmic volume to be coordinated/serviced, enabling the cell to be very long
4. Organised arrangement of actin and myosin filaments into sarcomeres/myofibrils generates force through the sliding-filament mechanism

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