If an ATP synthase contains 10 c subunits, 3 α subunits and 3 β subunits, how many protons must pass through this complex for every ATP molecule synthesized (assuming that all of the protons are used for ATP synthesis)?

Question

Quizplus · Accepted Answer

For every ATP synthesized, the number of protons required is determined by the number of c subunits in the ATP synthase complex. Each rotation of the c-ring, consisting of 10 c subunits in this case, synthesizes 3 ATP molecules (thanks to the 3 α and 3 β subunits). Therefore, to synthesize 1 ATP molecule, the c-ring must rotate 1/3 of a full rotation. Since 10 protons are needed for a full rotation (1 proton per c subunit), 10/3 protons are needed for 1/3 of a rotation, which equals approximately 3.3 protons per ATP molecule synthesized.

If an ATP Synthase Contains 10 C Subunits, 3 α