B Rotate to a (tilted) position to bind to actin. Explanation: The cycle begins with myosin tightly bound to actin (in the absence of ATP). Binding to ATP dissociates myosin from actin and hydrolysis of ATP induces a conformational change in myosin. This change affects the myosin neck region, which acts as a lever arm moving the myosin head group. ADP and phosphate attach to the myosin head, which attaches to the actin filament in a new position, releasing phosphate and releasing ADP. In this way, the myosin head resumes its initial conformation.
B. The release of calcium ions causes the binding of myosin and actin. This statement best describes a cause and its effects that occur during the process of muscle contraction. Muscle contraction can be explained by the sliding filament theory. 1. Muscle activation: The motor nerve generates an impulse to transfer signals from neurons to the neuromuscular junction. This stimulates the sarcoplasmic reticulum to release calcium into muscle cells. 2. Muscle contraction: Calcium in muscle cells binds to troponin, causing actin and myosin to bind. Actin and myosin in muscle bind and contract using ATP as an energy source.
B. The release of calcium ions causes the binding of myosin and actin. This statement best describes a cause and its effects that occur during the process of muscle contraction. Muscle contraction can be explained by the sliding filament theory. 1. Muscle activation: The motor nerve generates an impulse to transfer signals from neurons to the neuromuscular junction. This stimulates the sarcoplasmic reticulum to release calcium into muscle cells. 2. Muscle contraction: Calcium in muscle cells binds to troponin, causing actin and myosin to bind. Actin and myosin in muscle bind and contract using ATP as an energy source. Explanation:
A. The release of calcium ions causes the binding of myosin and actin. Skeletal muscle contraction occurs by induction of nerve impulses, which produce the movement and interaction of filaments containing proteins called actin and myosin. This interaction of filaments is regulated by proteins called tropomyosin and troponin present in actin filaments. The motor nerve causes the depolarization of the sarcolemma of the muscle membrane. This causes the sarcoplasmic reticulum to release calcium ions. This calcium binds to troponin and thus allows the tropomyosin strand on the actin filament to move so that the part of the actin where the myosin head should be attached remains uncovered. Binding of actin filament to myosin results in contraction. Thus, the release of calcium ions causes the union of myosin and actin and causes muscle contraction.
No, because tropomyosin cannot move until calcium ions bind to troponin Explanation: Tropomyosin can only move if calcium binds to troponin. This is because that is the main purpose of calcium in this system. Tropomyosin acts as a portal and prevents actin from binding to myosin. If the tropomyosin moves anyway, there is no need for calcium in the system. It is also important to consider that the stimulation of nerve impulses causes the calcium gates to open, causing a series of actions that lead to muscle contraction.
Answer 6
The correct answer is option B, that is, the release of calcium ions causes actin and myosin to combine. When a muscle contraction is stimulated, calcium is evacuated into the fibre. It combines with troponin and induces it to displace tropomyosin, exposing the myosin cross-bridge binding site. Thus, the face of the actin filament is now free to combine with the myosin heads to initiate muscle contraction.
Answer 7
When the stimulation of the motor neuron which gives the impulse to the muscle fibers ceases, the chemical reaction which causes the rearrangement of proteins in the muscle fibers stops. Explanation: This reverses the chemical processes in the muscle fibers and the muscle relaxes. i hope this helps you
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