Steps of Muscle Contraction — NEET Biology

Which of the following statements correctly describe the roles of various components during skeletal muscle contraction and relaxation? S1: The binding of Ca²⁺ to troponin leads to the removal of the masking of active sites for myosin on the actin filaments. S2: ATP hydrolysis provides the energy required for the myosin head to bind to actin and form a cross-bridge, as well as for the subsequent pulling of the actin filament. S3: A fresh molecule of ATP is essential for the detachment of the myosin head from the actin filament, thereby breaking the cross-bridge. S4: Muscle relaxation occurs when Ca²⁺ ions are actively pumped out of the sarcoplasm and back into the extracellular fluid, resulting in the masking of actin sites. S5: White muscle fibres are characterised by a high myoglobin content and abundant mitochondria, making them primarily dependent on aerobic respiration.