BIOL 201 Lecture 15: BIOL 201 cell biology and metabolism lecture 15
Document Summary
Muscle: muscle is an assembly of contractile bundles, a muscle fiber is a single muscle cell. E. g. type ii fiber the fast twitch fiber. Sliding filament theory muscle contraction: as muscle cell contracts, the overlap between thin (actin) and think (myosin) filaments increases, cross bridge cycle. Cross bridge refers to the connection between thick and thin filaments (the myosin head) Atp binding releases myosin head from actin. Atp controls the affinity of myosin with actin by changing the binding site shape. Hydrolysis of atp: myosin head rotates to cocked state strained conformation. The conformation of myosin head is highly reversible as the conversion between. Atp and adp, but without the actin filament in its position, myosin cannot bind. (actin filament is a twisted helix shape, not all actin unit is in the right orientation for binding) Tropomyosin sits on actin filament and blocks the binding site for myosin. When brain signal arrives, ca2+ ions are released from sarcoplasmic reticulum.
