Which of the following processes directly require ATP? Choose all that apply.

a. Diffusion of calcium into the motor neuron at the neuromuscular junction.

b. Release of cross-bridge (interaction) between actin and myosin.

c. Movement of calcium ions back into the sarcoplasmic reticulum after contraction.

d. Conformation change of troponin resulting in the movement of tropomyosin off the actin active sites.

Answer:the following processes directly require ATP includes:

B (Release of cross-bridge (interaction) between actin and myosin.)

C (Movement of calcium ions back into the sarcoplasmic reticulum after contraction.)

Explanation:

Muscle contraction occurs in various parts of the body to ensure proper body functioning. This process requires the release of calcium ion and the use of ATP (Adenosine Triphosphate) as source of energy at various levels for the process to take place. The distinct role of ATP in muscle contraction includes:

-ATP is directly required as it causes detachment from actin after power stroke when it binds at one of the reactive sites of myosin. This explains option B (Release of cross-bridge (interaction) between actin and myosin.)

-it powers the pump that transports calcium ions back into the sarcoplasmic reticulum after contraction. This explains option C (Movement of calcium ions back into the sarcoplasmic reticulum after contraction)

- it activates the myosin head so it can bind to actin and rotate by the action of ATpase enzyme.

B

Explanation:

During muscle contraction ATP separate to myosin-actin cross bridge, thus resealing the myosin and preparing it for the next contraction.

The mechanism of this process occurs when a a high-energy state ATP binds to myosin, resulting in ATP being hydrolyzed into ADP and phosphate. This breaking of ATP releases energy that alters the angle of the myosin head to a tilted position, thus exposing it, allowing for actin to bind to the head, for the next contraction to proceed.