Question

Explain the ultrastructure of myofibrils.

Answer 1

Myofibril

1. In mammals, a myofibril is a skeletal muscle component.
2. Myofibrils are long filaments that form muscle fibers by running parallel to one another.
3. Myofibrils and myofibers that result can be several centimeters long.
4. Muscular fibers are single multinucleated cells that make up muscle mass.
5. Myofibrils are made up of repeating subunits called sarcomeres.
6. Muscle contractions are controlled by these sarcomeres.

Myofibrils Structure

1. The two types of filaments are actin and myosin filaments.
2. Myosins are thick filaments made from 300 to 500 myosin molecules.
3. The head, neck, and tail of every myosin molecule are two strands.
4. The head has binding sites for actin and ATP molecules.
5. Thin filaments are actin filaments made from smaller actin proteins.
6. A filament of actin has 300-400 such proteins
7. When two actin filaments unite to form a helical shape, the F-actin filament is generated.
8. These filaments contain binding sites for myosin heads.
9. Troponin and tropomyosin are two extra proteins found in F-actin filaments which might be crucial.
10. Tropomyosin covers the region of myosin head binding when the muscle is relaxed.
11. The troponin protein has a clip-like structure that keeps the tropomyosin in place.
12. Muscle contraction and relaxation are controlled by the actin and myosin filaments.