What is the direct source of energy for ATP produced by ATP synthase?

What is the direct source of energy for ATP produced by ATP synthase?

• A. The NADH directly provides ATP
• B. Light energy
• C. The proton gradient
• D. The chemical energy from glucose

Answer: (C)

The direct energy source for ATP synthase is the proton gradient across the membrane, also known as the proton motive force. In respiration and photosynthesis, electron transport chains push protons across the membrane, creating a high H+ concentration on one side and an electrical potential. When protons flow back through ATP synthase, their movement drives the rotation of the enzyme’s rotor and induces conformational changes that synthesize ATP from ADP and inorganic phosphate. Light energy can initiate and sustain gradient formation in photosynthesis, but the energy actually used by ATP synthase is the stored gradient itself. Nutrients like glucose or carriers like NADH provide the energy to build that gradient, not the energy to power ATP synthase directly.

The direct energy source for ATP synthase is the proton gradient across the membrane, also known as the proton motive force. In respiration and photosynthesis, electron transport chains push protons across the membrane, creating a high H+ concentration on one side and an electrical potential. When protons flow back through ATP synthase, their movement drives the rotation of the enzyme’s rotor and induces conformational changes that synthesize ATP from ADP and inorganic phosphate. Light energy can initiate and sustain gradient formation in photosynthesis, but the energy actually used by ATP synthase is the stored gradient itself. Nutrients like glucose or carriers like NADH provide the energy to build that gradient, not the energy to power ATP synthase directly.