The Biochemistry of Movement > 9.7.5. Muscle cells cause movement by contraction along their length > Muscle Cell Contractions >
Identify the cause of the muscle cell contraction as the release of calcium ions after a nerve impulse activates the muscle cell membrane
- “Sliding filament theory”
- Ca2+ ions interact with tropomyosin and troponin, exposing the active sites on the actin filament and allowing the myosin head to bind there.
- This allows myosin to catalyse the hydrolysis of ATP, resulting in the energy release, which causes the myosin head to move into a higher energy state.
- The higher energy state permits the head to bind to an active site further along the actin/tropomyosin/troponin strand. This leads to the release of phosphate group and eventually ADP.
- When the nerve impulse ceases, the myosin head resumes its normal resting position.