Electron transport chain pumps protons out of the mitochondrial matrix. Intermembrane space ph ~ 7, matrix ph ~ 8; intermembrane more acidic therefore more protons. More protons in intermembrane space, they want to diffuse to lower concentration. Consequence of the fact that proteins are positive and there is no counter ion being moved across the membrane with them; accumulates a positive charge on the intermembrane space side of the inner mitochondrial membrane. Positives want to get into the more negative side membrane potential. Electrical potential contributes more strongly then the concentration difference. Chemeosmotic hypothesis: protonmotive force drives the synthesis of atp: destruction of proton gradient inhibits atp synthesis synthase. F1f0 atp: a protein complex that allows protons to flow down their electrochemical gradient. The energy from this proton movement is used to make atp; couples movement of protons to atp synthesis: atp is made in the matrix. 3b section with a subunit, allowing protons to be released into matrix.