BIOL 121 Lecture Notes - Lecture 22: Atp Hydrolysis, Neuromuscular Junction, Conformational Change
Document Summary
A muscle shortens and generates tension due to interaction between thick and thin filaments (cross bridge) Swiveling of myosin heads pulls thin filaments toward center of sarcomere. No change in thick or thin filament length (just bring the thin filaments closer together) Resting state: cycle begins with energized (cocked) myosin heads with adp and pi attached. When high intracellular ca2+ is present, myosin binding sites on actin are exposed, energized myosin heads binds to thin filaments. Myosin-actin binding triggers release of pi and adp. Triggering conformational change (powerstroke) of myosin head. Pulling the thin filament toward the center of the sarcomere. Atp binds to myosin head and releases head from actin. If no atp present, cross bridges cannot detach. Once detached: myosin head splits atp into adp and pi using energy to re-energize. Cycle continues as long as myosin binding sites are available on. Cross bridge cycle (continued) actin (as long as ca2+ stays high)
