ATP vs. ADP: What's the difference?

ATP (adenosine triphosphate) and ADP (adenosine diphosphate) refer to chemicals that are important to life, and are derived from each other as part of a cellular energy cycle. When ATP finds another phosphate, it releases energy and one of the phosphates splits off. This causes it to have only two phosphate molecules, turning it into ADP. When ADP encounters another phosphate, it merges with it, consuming energy in the process. This produces ATP.

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abbreviation, noun
  1. an ester of adenosine and triphosphoric acid, C10H12N5O4H4P3O9, formed especially aerobically by the reaction of ADP and an orthophosphate during oxidation, or by the interaction of ADP and phosphocreatine or certain other substrates, and serving as a source of energy for physiological reactions, especially muscle contraction.
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abbreviation, noun
  1. an ester of adenosine and pyrophosphoric acid, C10H12N5O3H3P2O7, derived from ATP, and serving to transfer energy during glycolysis.
  2. the processing of data by computers or related devices, using techniques that reduce human intervention to a minimum.

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