20. What condition is required for ATP synthase to move hydrogen down its gradient? A. More ATP molecules ahead of the hydrogen
than below it B. More hydrogen ions outside the membrane than inside it C. More hydrogen ions inside the membrane than outside it D. A day with 75 percent direct sunlight
This H+ ion gradient is referred to as a proton motive force. It is created using energy from the Krebs cycle in the matrix of the mitochondria. As electrons are passed from one protein complex to another, reducing molecules such as NADH and FADH2, the protons are pumped to the intermembrane space of the mitochondria. ATP synthase uses this potential to generate ATP as the H+ ions move downgradient (back to the matrix) through channels in the protein enzyme.
