ANATOMY

Detailed explanation-1: -ATP prepares myosin for binding with actin by moving it to a higher-energy state and a “cocked” position. Once the myosin forms a cross-bridge with actin, the Pi disassociates and the myosin undergoes the power stroke, reaching a lower energy state when the sarcomere shortens.

Detailed explanation-2: -The energy of the ATP hydrolysis is used for the bending of the actin-bound myosin (i.e., the bending of its S1 region). The bending is also called a power stroke. ATP molecules have high-energy phosphate bonds that power the bending of the S1 region in myosin.

Detailed explanation-3: -The power stroke requires the hydrolysis of ATP, which breaks a high-energy phosphate bond to release energy. Actin (red) interacts with myosin, shown in globular form (pink) and a filament form (black line).

Detailed explanation-4: -Muscle contraction occurs when sarcomeres shorten, as thick and thin filaments slide past each other, which is called the sliding filament model of muscle contraction. ATP provides the energy for cross-bridge formation and filament sliding.