During respiration most ATP is produced A - Scottish Highers Human Biology - Question 6 - 2017

During respiration, the majority of ATP is produced through a process called oxidative phosphorylation, which occurs in the inner membrane of the mitochondria. This process relies on the movement of protons (hydrogen ions) across the inner mitochondrial membrane.

As electrons are passed through the electron transport chain, they release energy that is used to pump hydrogen ions from the mitochondrial matrix into the intermembrane space. This creates a proton gradient, which stores potential energy.

The enzyme ATP synthase, embedded in the inner membrane, allows these hydrogen ions to flow back into the matrix. The energy released as hydrogen ions pass through ATP synthase drives the conversion of ADP and inorganic phosphate into ATP. Thus, the correct answer is that hydrogen ions are passed through the membrane protein ATP synthase, leading to ATP production.