NADPH is a molecule created during the oxidative phase of the pentose phosphate pathway. It is used in anabolic reactions, specifically in the formation of fatty acids. Another important role is that it acts as an anti-oxidant. Finally, NADPH is easily discriminated from NADH in the body because of an additional attached phosphate group. This allows the body to regulate the concentrations of the two similar molecules independently.

A dehydrogenase is an enzyme that removes hydrogen ions from a molecule, thereby oxidizing it.Lactate dehydrogenase converts lactate to pyruvic acid and NADH to NAD+ in glycolysis.The reaction is reversible, in which case it provides pyruvate for gluconeogenesis.Lactate dehydrogenase is present in most tissues with some isoforms more frequent than others. For example, isoenzyme LDH-1 is found in the heart, red blood cells, and brain.

Complex I (NADH-CoQ reductase) contains iron-sulfur proteins, and complex II (succinate-CoQ reductase) contains both heme and iron-sulfur proteins. Thus, iron deficiency would compromise the function of complex I and II. The other enzyme complexes do not have iron-containing proteins, thus, they would not be impaired by an iron deficiency.

Complex IV (cytochrome oxidase) contains two copper centers,  and , thus a copper deficiency would result in loss of function of enzyme complex IV. The other enzyme complexes do not contain copper, thus, they would not be impaired by a copper deficiency.

Complex II of the electron transport chain catalyzes the following reaction:

It uses the enzyme succinate dehydrogenase. The immediate result of this complex's loss of function would be a buildup of succinate, since that molecule can no longer be oxidized to fumarate. The multitude of problems that can arise come from this crucial step of the citric acid cycle not being able to move forward.

The conversion of succinate to fumarate is the only reaction that occurs outside of the normal Krebs cycle. Complex II of the electron transport chain has an enzyme known as succinate dehydrogenase. This enzyme is responsible for the conversion of succinate to fumarate. Fumarate is return to the cycle where it is then oxidized to malate continuing the cycle. Each of the other reactions of the Krebs cycle listed all occur in the inner mitochondrial matrix; whereas the conversion of succinate to fumarate occurs at the inner mitochondrial membrane.

ATP synthase uses the proton gradient across the inner membrane to generate ATP. The ATP synthase is essentially like a rotary motor. The proton gradient serves as the priming of the ATP synthase. As proton are moved from the outer mitochondrial matrix back into the mitochondrial matrix they are providing mechanical energy to turn the pump. As the pump is being turned ATP synthase utilizes a unit of ADP and inorganic phosphate to generate one molecule of ATP. This is done for every three turns of the ATP synthase.

Complex IV is also known as cytochrome c oxidase because it accepts the electrons from cytochrome c and directs them towards the four electron reduction of oxygen to form two molecules of water. ATP synthase is directly responsible for the generation of ATP by utilizing one unit of ADP and one unit of inorganic phosphate along with the proton motive force (PMF). Complex II is also known as succinate dehydrogenase which is responsible for one of the reaction of the Krebs cycle: succinate to fumarate. This reaction generates one molecule of . Complex I is also known as  dehydrogenase in that it oxidizes the coenzyme .

Complex I is also called NADH-Coenzyme Q (CoQ) reductase because it transfers 2 electrons from NADH to CoQ. Complex I was formerly known as NADH dehydrogenase. This complex binds NADH and takes up two electrons.The last step of this complex is the transfer of two electrons one at a time to CoQ. The process of transferring electrons from NADH to CoQ by complex I results in the overall transport of protons from the matrix side of the inner mitochondrial membrane to the inter membrane space where the hydrogen ion concentration increases generating a proton motive force which is utilized by ATP synthase.

Complex II of the electron transport chain is generally apart of both the electron transport chain as well as the Krebs cycle. It is the the succinate dehydrogenase that carried out the conversion of succinate to fumarate in the Krebs cycle. The only enzyme of the citric acid cycle that is an integral membrane protein. The conversion of succinate to fumarate generates an .  then transfers its electrons one at a time through complex II. The final step of this complex is the transfer of two electrons one at a time to coenzyme Q.