Question

Immediate source of energy for muscle contraction is
A.Glucose
B.GTP
C.Creatine phosphate
D.ATP

Answer 1

Muscles are composed of two major contractile proteins namely actin and myosin. Each actin is a thin filament having two F or filamentous actins. These filaments are helically bound to each other. Each myosin is a thick filament. It is a polymerized protein. The globular head of the myosin is an active ATPase enzyme that has sites for ATP to bind. It also has active sites for actin.

Complete step by step answer: 1.According to the sliding filament theory, muscle contraction takes place when the thin filaments slide over the thick filaments. A signal is sent via a motor neuron by the central nervous system and this initiates muscle contraction.
2.The generation of the action potential in the sarcolemma leads to the release of calcium ions in the sarcoplasm. An increase in the calcium levels leads to the removal of the masking of the active sites for myosin.
3.The energy which is released from ATP hydrolysis helps in the binding of the myosin head to the exposed active sites on action forming a cross-bridge.
4.When contraction of the muscles takes place, the I bands get reduced and the A bands remain the same.
5.The myosin goes back to its relaxed state after releasing ATP and inorganic phosphate.
6.A new ATP is now bound and the cross-bridge is broken. The myosin head again hydrolyses the ATP and the cross-bridge is again formed and broken causing further sliding.
7.Red fibers are a type of muscle contain mitochondria which helps them to utilize large amounts of oxygen for the production of ATP. These red fibers contain myoglobin which is a red-colored pigment used to store oxygen.
Thus, the immediate source of energy for muscle contraction is (D) ATP.

Note: 1.Thus, muscle proteins such as myosin and actin play vital roles in muscle contraction.
2.Myosin ATPase is considered to be the most important enzyme taking part in muscle contraction.