Sarcomere

Sarcomere: structure and function

The sarcomere is the basic structural and functional unit of skeletal and cardiac muscle. It is a section of myofibril - a microscopic fiber consisting of actin and myosin filaments that ensure muscle contraction.

The sarcomere is about 2 µm long and consists of two main protein structures - actin and myosin filaments, which form intersecting periodic stripes. Actin filaments are shaped like a double helix, while myosin filaments are shaped like two strands coiled together. Myosin filaments contain myosin heads, which can bind to and move along actin filaments, resulting in muscle contraction.

The sarcomere also contains other proteins, such as titin and nebulin, which help maintain myofibril structure and regulate its function. Titin is the largest protein in the human body and extends from the Z-line of the sarcomere to the M-line, providing the elasticity of the myofibril. Nebulin is involved in the assembly of actin filaments and regulates sarcomere length.

The function of the sarcomere is to convert the energy released by the cell into mechanical work. When a muscle contracts, actin and myosin filaments slide against each other, which leads to shortening of the sarcomere. This process occurs due to the hydrolysis of ATP, which provides energy for the movement of myosin heads.

In conclusion, the sarcomere is a key element in the structure of the muscle cell that enables its contraction and mechanical function. Its structure and function are carefully regulated by various proteins and enzymes, allowing the muscles to quickly and accurately respond to changing conditions.

Sarcomeres are the basic functional units of muscle tissue that contain myoglobin and myosin structure. These two components together are responsible for the contractile function of muscles. A sarcomere is also called a specially selected unit of a chain of molecules of the contractile protein actin; one link of this actin chain is called a sarcomere. The myosin molecule, which connects both actin and myosin into a central filament, attaches these two proteins to the Z-lines and separates the chains during contraction. To increase force, contracting muscle fibers are combined together into motor units with a strictly defined number of actin molecules. Each such unit includes a certain amount