Cristae are the inner folded membranes in mitochondria where enzymes and proteins involved in oxidative phosphorylation are located.

Releasing energy in stages allows more energy to be harvested for the benefit of the organism, rather than being released as heat.

Oxidative phosphorylation occurs in the inner mitochondrial membrane.

The electron transfer chain is a series of electron carrier molecules in the inner mitochondrial membrane.

The first electron carrier receives high-energy electrons from reduced NAD and reduced FAD. The electrons are passed along a series of electron carrier molecules, releasing energy as they are transferred.

Reduced NAD and reduced FAD are coenzymes that transfer hydrogen to the inner mitochondrial membrane during oxidative phosphorylation.

The hydrogen atoms dissociate into hydrogen ions (protons) and electrons.

In aerobic respiration, chemiosmosis is the diffusion of protons across the partially permeable inner mitochondrial membrane, down their electrochemical gradient through ATP synthase channels.

The movement of the protons releases energy that is used to synthesise ATP.

ATP synthase catalyses the production of ATP from ADP and P_i.

This uses the energy from the flow of protons down their concentration gradient from the intermembrane space into the mitochondrial matrix through ATP synthase channels.

Oxygen is the final acceptor of electrons at the end of the electron transport chain and combines with electrons and protons to form water.

Without oxygen as the final electron acceptor the reactions inside the mitochondrion stop, decreasing ATP production.

The energy is used to actively transport protons across the inner mitochondrial membrane from the mitochondrial matrix into the intermembrane space.