The movements of electrons between cellular reductants and oxidants represent another form of energy transfer in cells. A reductant (or reducing agent) is a substance that loses or donates electrons to another substance; the latter substance is the oxidant (or oxidizing agent). Conversely, an oxidant is a substance that accepts electrons from another substance, the latter being the reductant. Reactions [...]
Cells commonly employ either of two mechanisms to cause endergonic reactions to take place. One mechanism, illustrated above by the glycolysis example, is to create reactant and product concentrations that are markedly different from equilibrium values. This can be brought about either through the production of additional reactants or through the removal of products by drawing them into other cellular [...]
In all cells, most of the major energy changes and reaction couplings involve nucleotides. Although the cell draws on a number of different nucleotide pools, ATP → ADP + phosphate Exchanges are the most common. Other exchanges, such as ATP → AMP + pyrophosphate OTP → CDP + phosphate Occur, for example, during lipid metabolism, as do reactions. Uridine triphosphate [...]