Biology 2382B Study Guide - Midterm Guide: Rigor Mortis, Myosin, Atp Hydrolysis

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In the absence of atp, the myosin head is firmly attached to the actin filament. This state is very short lived in living muscle cells, it is the state responsible for muscle stiffness in death (rigor mortis) Step 1 on binding atp, the myosin head releases from the actin filament. Step 2 the head hydrolyzes the atp to adp and pi, which induces a rotation in the head with respect to the neck. This states stores the energy released by atp hydrolysis as elastic energy. Step 3 myosin in the cocked state binds actin. Step 5 the head remains tightly bound to the filament as adp is released and before fresh atp is bound by the head. A sarcomere is from one z-disk to the next. The a band contains thick myosin filaments; the i band contains no myosin, just actin. (-) end is inwards to myosin and (+) ends at z disk.