All Cellular Respiration processes begin with glycolysis to form pyruvate and NADH.
The synthesis of energy is driven by establishing ion gradients

Aerobic Respiration

Pyruvate molecules formed are transported into the inner mitochondrial membrane to form Acetyl CoA.
Acetyl CoA is then fed into the Tricarboxylic Acid Cycle (a.k.a. the Krebs cycle or the citric acid cycle).
- This metabolic pathway involves metabolites found in the cell’s other catabolic pathways.
- All of the cell’s energy providing molecules get broken down to metabolites of the TCA cycle.
- This reaction produces the coenzymes and which facilitate the formation of via Oxidative Phosphorylation.
Molecules such as -dinitrophenol uncouple ADP phosphorylation and glycolysis, effectively inhibiting ATP production.
- These molecules act as proton pumps which stabilizes the proton gradient.

Electron Transport Chain

ATP synthesis is performed using the coenzymes.
- This is done by using the high energy electrons from and in the Electron Transport Chain.
- Due to the ETC, protons are pumped outward across the inner mitochondrial membrane forming a proton electrochemical gradient .
  - The force that is produced by this gradient is called the proton motive force.
    - Aside from ATP synthesis, it also helps in moving around ADP and P in and out of the mitochondrion.
    - It also helps in pumping calcium ions.
  - The exact contribution of concentration and voltage to the proton motive force depends on the permeability of the inner membrane.
- Protons are then moved back across the membrane which drives the formation of ATP.
- This process is analogous to stretching a rubber band to store and then release energy.
The Electron Transport chain contains five types of membrane-bound electron carriers. Electrons lose energy as they travel across the chain.
- Flavoproteins
- Cytochromes - proteins with heme groups.
- Copper Atoms
- Ubiquinone
- Iron-sulfur proteins
The ETC contains four complexes based on the above carriers.
- Complex I - NADH Dehydrogenase
- Complex III - Cytochrome
- Complex II - Succinate Dehydrogenase
- Complex IV - Cytochrome oxidase
The final electron recipient in the Electron Transport Chain is .

One hypothesis is called the binding change mechanism
- The energy released by the movement of protons is not used to drive ADP phosphorylation directly but principally to change the binding affinity of the active site for the ATP product so that ATP can be released.
- Each active site in ATP synthase progresses successively through three distinct conformations that have different affinities for substrates and product.
- ATP is synthesized by rotational catalysis in which one part of the ATP synthase rotates relative to another part. The rotation itself is driven by proton movement.