How the mitochondrion makes ATP

The mitochondrion converts energy from food into ATP, the cell's usable energy currency, mostly through aerobic respiration.

The electron transport chain pumps protons across the inner membrane, creating a gradient (the proton-motive force).

ATP synthase lets protons flow back through it, and that flow drives the mechanical synthesis of ATP from ADP.

Check yourself

In your own words: why does the cell bother building a proton gradient instead of making ATP directly?

Practice (self-check, not graded)

1. What gradient does the electron transport chain build?

2. What enzyme actually synthesizes ATP?

3. Roughly where does aerobic respiration occur in the cell?