Question

If a muscle cell is unable to produce any more ATP, which of the following would happen as a result?

SELECT ALL THAT APPLY

Calcium ions cannot be pumped back into the sarcoplasmic reticulum

Cross-bridges cannot break

Cross-bridges cannot form

Calcium cannot bind to troponin

Answer 1

Answer are -1) calcium uon cannot be pumped back into the sarcoplasmic reticulumn.

2)cross bridges cannot break

As neurotransmitter arises at the muscle end plate and bonds to receptors present at neuromuscular junction which further allows ions transport across the sarcolemma and generates and action potential. This action potential is mediated through T tubules in the Sarcomere and stimulates release of calcium from sarcoplasmic reticulumn.

The calcium so released binds to troponin and detaches troponin- tropomyosin complex and unmasks the binding sites on myosin filament for actin filament. Cross bridge formation takes place.

This is carried on by cross bridge formation where acting filament slides over myosin filament by rachet like action and gets shortened to bring contraction in muscle. After one cycle , this cross bridge breaks with the hydrolysis of ATP into ADP which provides energy for cross bridge breaking and brings myosin head in cocked position.

After contraction,Calcium ions are pumped back into the sarcoplasmic reticulumn with the help of a protein which requires ATP to pump the calcium ions, it results into relaxation. Actin binding sites on myosin are covered by tropomyosin, tension in the fiber is lost and relaxation occurs.