Question

The sequence of crossbridge formation and myofilament movement will be repeated as long as _____ ____ are present

Answer 1

The crossbridge formation and myofilament movement in muscle fibers continue as long as there are sufficient calcium ions and ATP available to support the contraction cycle.

Step-by-step explanation:

The sequence of crossbridge formation and myofilament movement will be repeated as long as calcium ions and ATP are present. During muscle contraction, the crossbridge cycle involves the myosin head pulling the actin filament, then detaching, re-cocking, and attaching again to continue the motion. This requires energy in the form of ATP. The cycle is initiated by the binding of calcium ions to troponin, which exposes the binding sites on actin for myosin heads to attach and form crossbridges, leading to muscle fiber contraction.

Answer 2

The crossbridge formation and myofilament movement continue as long as there are calcium ions and ATP. Calcium ions enable the binding of myosin heads to actin sites, while ATP provides the necessary energy for myosin heads to reset and for muscle contraction to occur.

Step-by-step explanation:

The sequence of crossbridge formation and myofilament movement will be repeated as long as calcium ions and ATP are present. In muscle contraction, the crossbridge cycling is a series of events where myosin heads, which are part of the thick filaments, pull on actin, which is part of the thin filaments. This is akin to the motion of oars while rowing a boat, where each cycle requires energy provided by ATP. Calcium ions bind to troponin, which allows this process to continue. When calcium is present, the myosin heads are able to attach to the actin binding sites, perform a power stroke by pulling the actin, and then detach before re-cocking for another cycle.

The availability of calcium and ATP are crucial for this process, as the cross-bridge muscle contraction cycle is triggered by calcium binding to the actin active site. Each power stroke causes a sliding movement of the actin over the myosin, leading to muscle contraction. The crossbridge cycle will repeatedly occur as long as these conditions are met, allowing the muscle fiber to contract and work effectively.