BIOL273 Study Guide - Final Guide: Myasthenia Gravis, Rigor Mortis, Myosin Head
14 Apr 2015
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Cross bridge at 45 degrees, myosin tightly bound to actin. Atp binds to binding site on myosin -> myosin released from actin. Myosin atpase hydrolyses atp --> adp + pi. Myosin head rotates on hinge, pulling thin actin filament along towards m line, uses atp (power stroke) Power stroke begins when tropomyosin moves off binding site. Myosin releases adp -> step 1 again. Relaxed muscles: waiting for ca2+ signal to move tropomyosin out of the way. If all cross bridges released together, thin filaments would slip back into their original position and contraction of muscle would not occur. When the cross bridge is at 45 degrees and no nucleotide is bound. Rigor mortis: stiffening of the body after death caused by lack of oxygen reduced levels of atp causes cross bridge to be stuck at step 1 eventually subsides because tissues break down and snaps cross bridges.
