IMED1001 Study Guide - Final Guide: Sliding Filament Theory, Myosin Head, Myosin
Document Summary
Thick filaments are comprised of many myosin molecules. Each actin filament is contacted by 3 myosin filaments. Each myosin filament contacts 6 actin filaments. A bands do not change in length. Actin thin filaments slide past myosin thick filaments. Automatic rotation of the myosin head pulls actin filament. Accompanied by adp dissociation at the nucleotide binding site. These rearrangements at active site give 5-10 nm displacement per stroke. Cross-bridges are made and broken with successive actin binding sites. Thereby pulling the actin filaments relative to the myosin. As these are anchored to the z~lines. The sarcomere effectively shortens, resulting in muscle contraction. Myosin head attaches reversibly to high affinity active sites on the actin thin filament. Myosin power stroke" pulls actin filament, contracting sarcomere. Atp hydrolysis drives re-cocking of myosin to high energy state. But is not required for power stroke. The lever movement pulls on the actin filament. Relative to the myosin head (~5-10 nm) producing force.
