Question

Describe the structure of the sarcomere: Z disc, H zone, I band, A band, M line, thick filaments, thin filaments, actin, myosin, titan

A) The H zone contains overlapping thick and thin filaments during muscle contraction
B) The Z disc is the center of the sarcomere, where myosin filaments anchor
C) The M line separates the I band into two halves
D) Titan is a protein that anchors thin filaments to the Z disc

Answer 1

The sarcomere is the functional unit of the muscle fiber. It is composed of a thin filament made of actin and a thick filament made of myosin. The sarcomere is bordered by structures called Z-discs, which anchor the actin myofilaments.

Step-by-step explanation:

The sarcomere is the functional unit of the muscle fiber. The sarcomere itself is bundled within the myofibril that runs the entire length of the muscle fiber and attaches to the sarcolemma at its end. As myofibrils contract, the entire muscle cell contracts. Because myofibrils are only approximately 1.2 µm in diameter, hundreds to thousands (each with thousands of sarcomeres) can be found inside one muscle fiber. Each sarcomere is approximately 2 µm in length with a three-dimensional cylinder-like arrangement and is bordered by structures called Z-discs, to which the actin myofilaments are anchored. Because the actin and its troponin-tropomyosin complex form strands that are thinner than the myosin, it is called the thin filament of the sarcomere. Likewise, because the myosin strands and their multiple heads have more mass and are thicker, they are called the thick filament of the sarcomere.