Why contraction requires ATP
Repeated muscle contraction depends on a supply of ATP. During the cross-bridge cycle, energy is needed to return myosin heads to the position from which another interaction with actin can occur.
Maintaining ATP availability
ATP used by contracting muscle can be supplied in three ways:
- Aerobic respiration contributes when there is an adequate oxygen supply.
- Anaerobic respiration can provide a small ATP yield very rapidly.
- Phosphocreatine can rapidly replenish ATP for a short period.
These sources differ in the rate at which they can support ATP demand and the length of time for which they are useful.