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3.6 Organisms respond to changes in their internal and external environments
Quick questions on Skeletal muscle contraction: the sliding filament theory and the sarcomere - AQA A-Level Biology
6short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is structure of skeletal muscle?Show answer
A skeletal muscle is made of many muscle fibres, each a long cell with many nuclei (a syncytium) and a shared cytoplasm called the sarcoplasm containing many mitochondria and an extensive sarcoplasmic reticulum (a store of calcium ions). Each fibre contains many myofibrils, the contractile units, arranged in parallel.
What is ultrastructure of the sarcomere?Show answer
A myofibril is divided into repeating units called sarcomeres, which give skeletal muscle its striped (striated) appearance. Within a sarcomere:
What is the sliding filament theory?Show answer
Muscle contraction is explained by the sliding filament theory: the actin and myosin filaments slide past each other, shortening the sarcomere without the filaments themselves changing length. The roles of calcium and ATP are central.
What is q1?Show answer
Describe the role of calcium ions in muscle contraction. [3 marks]
What is q2?Show answer
Explain what happens to the I band, H zone and A band of a sarcomere when a muscle contracts. [3 marks]
What is q3?Show answer
Compare slow and fast twitch muscle fibres. [3 marks]
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