Question

the functional unit of a skeletal muscle fiber is the

myofilament.

sarcolemma.

myofibril.

sarcoplasmic reticulum.

sarcomere.

Explanation:

• Myofilament: These are the protein filaments (actin and myosin) within a myofibril. They are part of the contractile machinery but not the functional unit.
• Sarcolemma: This is the plasma membrane of a muscle fiber. It is involved in the conduction of electrical impulses but not the functional unit for contraction.
• Myofibril: These are long cylindrical structures within the muscle fiber made up of sarcomeres. While important for muscle structure, the sarcomere is the functional unit.
• Sarcoplasmic reticulum: This is a specialized endoplasmic reticulum in muscle cells that stores and releases calcium ions. It is not the functional unit.
• Sarcomere: It is the basic functional unit of a skeletal muscle fiber. It is the repeating unit between two Z - lines and is responsible for muscle contraction as the actin and myosin filaments within it interact.

Answer:

sarcomere.