Cell Respiration Vocab Acetyl Coenzyme A??-? A small molecule that carries acetyl functional groups in cells. Composed of an acetyl group attached to a coenzyme A molecule. The starting product of the citric acid cycle. Adenosine Triphosphate (ATP)??-? The molecule from which cells derive energy. Comprised of an adenosine molecule bonded to three phosphates, each phosphate bond contains energy, especially the third bond. By breaking that one bond and reducing ATP to adenosine?diphosphate (ADP), the cell can get the energy to carry out its various processes. Aerobic respiration??-? A metabolic process involving oxygen in the breakdown of glucose.