3.5 Energy-rich functional groups in substrates of glycolysis
You will have heard that the most abundant and important energy-
rich metabolite in the cell is ATP. Within this molecule, the
energy is stored in the energy-rich phosphodiester bonds.
Cleavage of these bonds is exergonic, and the energy released in
the cleavage drives the various reactions and processes powered
by ATP. Conversely, in creating ATP from ADP, we require energy
to form a new phosphodiester bond. We just saw where this energy
is derived from in phosphoenolpyruvate, and we may say that the
enolphosphate group is another energy-rich group. The first ATP
in glycolysis is formed by cleavage of the carboxyphosphate
mixed anhydride in 1,3-bisphosphoglycerate, and so we may infer
that such mixed anhydrides are energy-rich groups as well.
Indeed, the same group also occurs in acetylphosphate and in
succinylphosphate, and both of these are capable as well to
drive the synthesis of a phosphodiester bond in ATP or GTP. If
we look again at Figure 3