The ultrastructure of a myofibril
A myofibril is a long, cylindrical strand inside a muscle fibre. It contains repeating units called sarcomeres, which are the sections that actually shorten when a muscle contracts.
Real World
When scientists use electron microscopes to examine beef steak, they can see the repeating sarcomere pattern — the alternating light (I) and dark (A) bands that give skeletal muscle its 'striped' or striated appearance.
Exam Focus
Label diagrams precisely — distinguish Z-lines, M-lines, A-bands, I-bands, and H-zones; examiners award each structural term separately.
Evaluation Scaffold
A four-step framework for high-quality evaluation. Use this for 'assess', 'evaluate', and 'to what extent' questions.
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