1. Dioxygen (O₂), sometimes referred to as oxygen, is used by aerobic organisms as a terminal electron acceptor in energy generation. Several physical and chemical properties of oxygen make it suitable for this role. In addition to its ready availability (it occurs almost everywhere on the Earth's surface), oxygen diffuses easily across cell membranes and it is highly reactive so that it readily accepts electrons.

2. The NADH and FADH₂ molecules produced in glycolysis, the β-oxidation pathway, and the citric acid cycle generate usable energy in the electron transport pathway. The pathway consists of a series of redox carriers that receive electrons from NADH and FADH₂ . At the end of the pathway the electrons, along with protons, are donated to oxygen to form H₂O.

3. During the oxidation of NADH, there are three steps in which the energy loss is sufficient to account for ATP synthesis. These steps, which occur within complexes I, III, and IV, are referred to as sites I, II, and III, respectively.

4. Oxidative phosphorylation is the mechanism by which electron transport is coupled to the synthesis of ATP. According to the chemiosmotic theory, the creation of a proton gradient that accompanies electron transport is coupled to ATP synthesis.

5. The complete oxidation of a molecule of glucose results in the synthesis of 29.5 to 31 molecules of ATP, depending on whether the glycerol phosphate shuttle or the malate-aspartate shuttle transfers electrons from cytoplasmic NADH to the mitochondrial ETC.

6. The use of oxygen by aerobic organisms is linked to the production of ROS. ROS form because the diradical oxygen molecule accepts electrons one at a time. Examples of ROS include the superoxide radical, hydrogen peroxide, the hydroxyl radical, and singlet oxygen. The danger from the highly reactive ROS is usually kept to a minimum by cellular antioxidant defense mechanisms.