Electron Carriers

Electron carriers are compounds that shuttle around high energy electrons, via redox reactions - the coordinating states of oxidation and reduction, respectively, losing and gaining these negatively charged particles.

For instance, one principal electron carrier is nicotinamide adenine dinucleotide, or NAD⁺ named so because, at the first carbon position, one ribose ring has an adenine base, while the other has a nicotinamide. At the fifth carbon position, two phosphate groups join these two nucleotides.

During metabolism, NAD⁺, as a coenzyme, binds to an enzyme, such as dehydrogenase, and acts as an oxidizing agent, removing two hydrogen protons, along with a pair of electrons from the reactant.

The electrons are then transferred to the positively charged nitrogen, and the hydrogen attaches to the opposite carbon, reducing NAD⁺ into NADH.

In the end, the extra hydrogen proton is left in the cytoplasm, and NADH shuttles its electrons to the mitochondrial membranes, where they enter the electron transport chain, and the carriers can continue to undergo redox reactions.