Search results
Results from the WOW.Com Content Network
Cross-bridge theory states that actin and myosin form a protein complex (classically called actomyosin) by attachment of myosin head on the actin filament, thereby forming a sort of cross-bridge between the two filaments. The sliding filament theory is a widely accepted explanation of the mechanism that underlies muscle contraction.
Cross-bridge cycle. Cross-bridge cycling is a sequence of molecular events that underlies the sliding filament theory. A cross-bridge is a myosin projection, consisting of two myosin heads, that extends from the thick filaments. [1] Each myosin head has two binding sites: one for adenosine triphosphate (ATP) and another for actin.
The binding of the myosin head to actin is known as a cross-bridge. A molecule, called adenosine triphosphate (ATP) which is produced by an intracellular structure called a mitochondrion, is then used, as a source of energy, to help move the myosin head, carrying the actin. As a result, the actin slides across the myosin filament shortening the ...
For a muscle cell to contract, tropomyosin must be moved to uncover the binding sites on the actin. Calcium ions bind with troponin C molecules (which are dispersed throughout the tropomyosin protein) and alter the structure of the tropomyosin, forcing it to reveal the cross-bridge binding site on the actin.
In invertebrate smooth muscle, contraction is initiated with the binding of calcium directly to myosin and then rapidly cycling cross-bridges, generating force. Similar to the mechanism of vertebrate smooth muscle, there is a low calcium and low energy utilization catch phase.
The myosin head is the part of the thick myofilament made up of myosin that acts in muscle contraction, by sliding over thin myofilaments of actin.Myosin is the major component of the thick filaments and most myosin molecules are composed of a head, neck, and tail domain; the myosin head binds to thin filamentous actin, and uses ATP hydrolysis to generate force and "walk" along the thin filament.
A cross-section of the pons divides it into a ventral and a dorsal area. The ventral pons is known as the basilar part, and the dorsal pons is known as the pontine tegmentum. [3] The ventral aspect of the pons faces the clivus, with the pontine cistern intervening between the two structures.
Most myosin molecules are composed of a head, neck, and tail domain.. The head domain binds the filamentous actin, and uses ATP hydrolysis to generate force and to "walk" along the filament towards the barbed (+) end (with the exception of myosin VI, which moves towards the pointed (-) end).