(adenosine diphosphate) A diphosphorylated nucleoside with the same structure as adenosine monophosphate but with a second phosphate linked through a * high-energy phosphate bond to the first. In photophosphoryla-tion ADP combines with another phosphate molecule to form ATP. This conversion is a major mechanism for the conservation of the light energy absorbed in photosynthesis. In some plants ADP acts as a sugar carrier, forming such molecules as ADP-glucose and ADP-sucrose. These ADP-sugars can then be oxidized to give energy or used in the synthesis of starch and ascorbic acid. See nucleoside diphosphate sugars . |
