Muscle contraction

Did you mean: types of muscle contraction

Myosin, ATP and muscle contraction

Skeletal muscle can be compared to a motor, capable of converting the chemical energy, supplied by ATP, into mechanical energy, acting on the skeletal lever system with good efficiency (no more than 30-50% of this energy is dissipated as heat). The result of this endoergonic reaction is muscle contraction.

Each myosin molecule has two binding sites, one for an ATP molecule and one for actin. Its ATPase activity allows it to hydrolyze ATP to ADP + inorganic phosphate and to use the energy thus developed to generate the movement. Everything happens with a cycle of molecular events:

1. The anchoring of ATP in the specific binding site on the myosin head leads to the detachment of the latter from the G-Actin molecule
2. The ATP, bound to the myosin head, is hydrolyzed to ADP and inorganic phosphate (Pi); both products remain anchored here; the presence of magnesium seems necessary to allow this reaction.
3. The energy released by the hydrolysis of ATP induces a rotation of the myosin head which, being charged with potential energy, weakly binds to a molecule of G-actin at an angle of 90 °.
4. The release of the inorganic phosphate causes a conformational change in the myosin head, generating the so-called whiplash. The rope (the actin filament) is thus pulled towards the center of the sarcomere, i.e. towards the M line.
5. The myosin head also releases the ADP molecule and remains tightly anchored to the actin, in a state of rigor that lasts only a few moments, before the cycle begins again with the umpteenth myosin-ATP bond.

Other articles on "Muscle Contraction"

1. actin myosin
2. muscles of the human body
3. Skeletal muscle
4. Muscles classification
5. Muscles with parallel bundles and pinnate muscles
6. Muscle anatomy and muscle fibers
7. myofibrils and sarcomeres
8. muscle innervation
9. neuromuscular plaque