∞ generated and posted on 2016.12.04 ∞
The product of ATP hydrolysis.
ADP stands for Adenosine DiPhosphate since ADP contains two ("Di") phosphate groups rather than ATP's three.
The actual hydrolysis chemical reaction involves ATP + H2O → ADP + Pi + energy.
This chemical reaction is not spontaneously reversible but instead requires a substantial input of energy is required to convert ADP back to ATP. See glycolysis, cellular respiration, and photosynthesis for discussions of this latter process. See also energy coupling.
Figure legend: The structure of ADP, Adenosine DiPhosphate. Note the two phosphate groups, linked together, versus ATP's three. Note also the nitrogens (N) found in adenosine, a nitrogenous base. Note that the corner of each of the geometric shapes represents a carbon atom and that each carbon atom has four bonds to it, with any missing bonds assumed to be hydrogen atoms that are not shown.
Figure legend: The structure of ATP, Adenosine TriPhosphate. Note the three phosphate groups, linked together, versus ADP's two. Note also the nitrogens (N) found in adenosine, a nitrogenous base. The corner of each of the geometric shapes represents a carbon atom and that each carbon atom has four bonds to it, with any missing bonds assumed to be hydrogen atoms that are not shown.
Figure legend: Energy coupling in organisms is typically illustrated based on the generation and hydrolysis of ATP. Energy generation is driven by whatever an organism utilizes as an energy source whereas the ATP, once produced, is used to power the organism. The figure presented shows the structures of ATP and ADP but not the water molecule involved in hydrolysis as well dehydration synthesis, nor the inorganic phosphate (Pi) that is added to ADP to produce ATP.
ADP is not the only hydrolytic breakdown product of ATP since ATP can also be hydrolyzed such that two phosphate groups are released simultaneously and still attached to one another, a product known as pyrophosphate. The other product of this reaction, besides energy, is known as AMP, which stands for Adenosine MonoPhosphate.
See also ATP hydrolysis.