PHGY 209 Lecture Notes - Lecture 23: Atp Hydrolysis, Conformational Change, Hydrolysis
21 Feb 2018
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Document Summary
Thin filaments (actin) and thick filaments (myosin) overlap in the a-band. The myosin filaments have heads at the end which interact with the actin. During contraction, the heads (forming cross-bridges) undergo cycles where they grab, pull, and release the actin. The random occurrences of these cycles among each myosin filament is what causes the contraction of sarcomeres. The cross-bridge cycle is driven by atp binding and hydrolysis by the myosin head groups. The myosin head must be able to reach out, bind, snap back, and let go of the actin filaments. The myosin head is an atpase which uses the energy from atp hydrolyses. As long as the muscle is activated and there is a sufficient atp supply, this cycle will continue for each myosin head. This occurs because the cells stop producing atp. When the atp depletes, there is no longer a source that will cause the myosin head to release the pulled actin filaments.
