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Question:

Which of the following does NOT describe a sarcomere?

A It completely surrounds the muscle fiber.
Explaination

The sarcomere is the contractile unit of a muscle made up of fibrous protein filaments, actin and myosin. During contraction, the sarcomere shortens in length when actin and myosin slide past each other. The structure that surrounds the muscle fiber is called the sarcolemma.