Yes, the ATPase activity in myosin molecules is located in the globular head region. This ATPase activity is essential for the cross-bridge cycling during muscle contraction, where ATP hydrolysis provides the energy for the myosin head to bind and release actin filaments.
Actin and myosin are proteins. Protein is a broad category of molecules.
myosin molecules
Molecules attached to the myosin head from the previous movement cycle are inorganic phosphate and ADP (adenosine diphosphate). These molecules are released when the myosin head binds to actin, leading to the power stroke of muscle contraction.
ATP not ADP binds to actin-myosin and is cleaved by to ADP.
Yes, myosin filaments are found in the A band of a sarcomere, which is a structural unit of a muscle cell. The A band contains both myosin and actin filaments and is located in the middle of the sarcomere.
ATP (--> ADP+Pi) and actin
The energy on the myosin head comes from ATP (adenosine triphosphate) molecules. When ATP is hydrolyzed, it releases energy that is used to power the movement of the myosin head during muscle contraction.
Ca2+
No, the heads of myosin molecules do not contact the actin filaments when a muscle is relaxed. In a relaxed state, the binding sites on actin are blocked by tropomyosin, preventing myosin heads from attaching. When calcium ions are released during muscle contraction, they bind to troponin, causing a conformational change that moves tropomyosin and exposes the binding sites for myosin, allowing contraction to occur.
Myosin is a protein found in muscle cells that plays a key role in muscle contraction. It consists of long molecules called myosin filaments, which interact with actin filaments to generate the force needed for muscle movement.
Regulatory molecules are commonly types of proteins which will regulate the functions of the muscles. The interaction of actin and myosin is regulated which will trigger muscle contraction.