The main purpose of the electron transport chain is to

How many $ATP$ molecules are produced during oxidative phosphorylation from one molecule of $NADH + H^+$ and $FADH_2$ respectively?

The chemiosmotic theory of oxidative phosphorylation suggests that adenosine triphosphate $(ATP)$ is produced because:

Given below are two statements.
$Statement-I$: During aerobic respiration, $ETS$ releases energy in a stepwise manner to prevent damage to cells.
$Statement-II$: During aerobic respiration, $ETS$ provides water molecules.
In the light of the above statements, choose the correct answer from the options given below.

$A$ : $2,4-DNP$ $(2,4-Dinitrophenol)$ is an uncoupling agent of $ETS$.
$R$ : It is soluble in lipids.

Which of the following contains both iron and copper?