(N/A) The energy released during the electron transport system is utilized in synthesizing $ATP$ with the help of $ATP$ synthase (complex $V$).
This complex consists of two major components,$F_{0}$ and $F_{1}$.
The $F_{1}$ headpiece is a peripheral membrane protein complex and contains the site for the synthesis of $ATP$ from $ADP$ and inorganic phosphate $(ADP + Pi \rightarrow ATP)$.
$F_{0}$ is an integral membrane protein complex that forms the channel through which protons cross the inner membrane.
The passage of protons through the channel is coupled to the catalytic site of the $F_{1}$ component for the production of $ATP$.
For each $ATP$ produced,$2 H^{+}$ ions pass through $F_{0}$ from the intermembrane space to the matrix,moving down the electrochemical proton gradient.
Thus,$ATP$ is synthesized.