Question

What is the function of cross-bridges in muscle contraction?

a) To connect myosin filaments to actin filaments
b) To generate heat during contraction
c) To maintain cell shape
d) To transport nutrients in and out of the cell

Answer 1

The function of cross-bridges in muscle contraction is to connect myosin filaments to actin filaments, facilitating the sliding movement that leads to the muscle shortening and contracting.

Step-by-step explanation:

The function of cross-bridges in muscle contraction is to connect myosin filaments to actin filaments. This connection is crucial for the process of muscle contraction, as outlined in the following steps:

• Calcium ions (Ca++) binding to troponin cause the exposure of the active sites on actin filaments.
• Myosin heads bind to these exposed actin-binding sites, forming a cross-bridge.
• During the power stroke, the myosin heads pivot, pulling the actin filaments towards the center of the sarcomere.
• ATP binds to the myosin head, causing the cross-bridge to detach.
• Hydrolysis of ATP relocks the myosin head, preparing it for another cycle of cross-bridge formation and movement.

This series of events known as the cross-bridge cycle is a process by which the actin and myosin filaments slide past each other, leading to the shortening of the muscle fiber and muscle contraction. ATP is necessary for cross-bridge formation and the sliding of filaments, and it is the energy source for this entire process.