How much energy does one ATP molecule provide?

How much energy does one ATP molecule provide?

• A. For multiple cross-bridges
• B. Only for nerve impulses
• C. Enough energy for one actin and one myosin cross bridge
• D. For heat production

Answer: (C)

The energy from one ATP molecule powers a single cross-bridge cycle between actin and myosin. When ATP is hydrolyzed, the myosin head is cocked into a high-energy position. As the myosin binds to actin and releases Pi, the energy stored in that head drives the power stroke, sliding the actin filament. After the stroke, ADP is released, and a new ATP can bind to detach the myosin head and reset it for another cycle. Because each cycle uses one ATP, one molecule provides enough energy for one actin–myosin cross-bridge event, even though many such events may occur simultaneously across a muscle fiber. The other options don’t fit: ATP isn’t reserved specifically for nerve impulses, and while some energy ends up as heat, the primary role of ATP hydrolysis here is to power a single cross-bridge cycle.

The energy from one ATP molecule powers a single cross-bridge cycle between actin and myosin. When ATP is hydrolyzed, the myosin head is cocked into a high-energy position. As the myosin binds to actin and releases Pi, the energy stored in that head drives the power stroke, sliding the actin filament. After the stroke, ADP is released, and a new ATP can bind to detach the myosin head and reset it for another cycle. Because each cycle uses one ATP, one molecule provides enough energy for one actin–myosin cross-bridge event, even though many such events may occur simultaneously across a muscle fiber. The other options don’t fit: ATP isn’t reserved specifically for nerve impulses, and while some energy ends up as heat, the primary role of ATP hydrolysis here is to power a single cross-bridge cycle.