Crista

  Cristae (singular crista) are the internal compartments formed by the inner membrane of a aerobic respiration since the mitochondria requires oxygen) to occur.

Electron transport chain of the cristae

ATP synthase harnesses the potential energy from the concentration gradient formed by the amount of H⁺ ions. H⁺ ions passively pass into the mitochondrian matrix by the ATP synthase, and later on help to reform H₂O.

The ATP synthase and the electrons that had traveled through the electron transport chain. As a result they form two molecules of water (H₂O). By accepting the electrons, oxygen allows the electron transport chain to continue functioning.

The electrons from each NADH molecule can form a total of 2.5 ATPs from ADPs and phosphate groups through the electron transport chain, while each FADH₂ molecule can produce a total of 1.5 ATPs. As a result, the 10 NADH molecules (from glycolysis, the efficiency for the electron transport chain is about 65%, as compared to only 3.5% efficiency for glycolysis alone.

Usefulness

The cristae greatly increase the surface area on which the above mentioned reactions take place. If they were absent, the inner membrane would be reduced to a single spherical shape, and with less reaction surface available, the reaction efficiency would be likewise reduced. Therefore, cristae are a necessity for the mitochondria to function efficiently.