Question

Consider an ATP synthase having twelve C-rings to sense proton motive force. The average number of protons required per ATP synthesis is _ _ _. (in integer)

Hint:

For ATP synthase: \[ \text{Protons per ATP} = \frac{\text{Number of }c\text{-subunits}}{3} \] because one full rotation generates \(3\) ATP molecules.

Answer 1

Correct Answer: 4

Step 1: How ATP synthase works.
Protons flow through the $F_0$ rotor and spin the c-ring, and that spin drives the $F_1$ head to make ATP.

Step 2: ATP per full turn.
One complete turn of the rotor produces $3$ ATP, because the $F_1$ head has three catalytic sites.

Step 3: Protons per full turn.
With twelve c-subunits, one full turn needs $12$ protons to pass.

Step 4: Protons per ATP.
\[ \frac{12\ \text{protons}}{3\ \text{ATP}} = 4\ \text{protons per ATP} \]

Step 5: Answer.
\[ \boxed{4} \]