What are the differences between ADP and ATP?

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Accepted Answer

ADP and ATP are molecules that contain stored chemical energy to be used by the cells. Despite this common function, there are a few notable differences between the two in terms of their physical properties as well as their biochemical roles in the human body.

Basis for comparison
ADP
ATP

Full Name
Adenosine Di Phosphate
Adenosine Tri Phosphate

Number of phosphate groups
Contains 2 phosphate groups
Contains 3 terminal phosphate groups

Cehmical formula
C10H15N5O10P2
C10H16N5O13P3

Chemical composition
Composed of 1 adenine molecule, a ribose sugar and two phosphate groups
Composed of 1 adenine molecule, a ribose sugar and three phosphate groups

Method of generation
Generated as a result of de-phosphorylation of ATP molecule by enzymes known as ATPases
Generated as a result of photophosphorylation, aerobic respiration, and fermentation in biological systems

Energy state of molecule
Is the lower-energy molecule of the two because of the absence of the high-energy pyrophosphate bond 
Is the higher-energy molecule of the two because of the presence of the pyrophosphate bond- a high-energy bond between the last two phosphates

Molar mass
427.201 g/mol
507.18 g/mol

Energy releasing mechanism
ADP + H2O → AMP + PPi  
ATP + H2O → ADP + Pi

Functions

Crucial to the flow of energy in living beings
Plays a role in catabolic pathways such as citric acid cycle, oxidative phosphorylation, and glycolysis
Activation of blood platelets to initiate healing of a broken blood vessel
Plays a key role in mitochondrial ATP synthase complex

Main energy carrier molecule in living beings
Metabolism in cells
Active transportation of molecules
Plays a role in cell signaling
Activation of amino acid
Helps maintain cell structure
Synthesis of macromolecules such as DNA, RNA, and proteins

Basis for comparison	ADP	ATP
Full Name	Adenosine Di Phosphate	Adenosine Tri Phosphate
Number of phosphate groups	Contains 2 phosphate groups	Contains 3 terminal phosphate groups
Cehmical formula	C10H15N5O10P2	C10H16N5O13P3
Chemical composition	Composed of 1 adenine molecule, a ribose sugar and two phosphate groups	Composed of 1 adenine molecule, a ribose sugar and three phosphate groups
Method of generation	Generated as a result of de-phosphorylation of ATP molecule by enzymes known as ATPases	Generated as a result of photophosphorylation, aerobic respiration, and fermentation in biological systems
Energy state of molecule	Is the lower-energy molecule of the two because of the absence of the high-energy pyrophosphate bond	Is the higher-energy molecule of the two because of the presence of the pyrophosphate bond- a high-energy bond between the last two phosphates
Molar mass	427.201 g/mol	507.18 g/mol
Energy releasing mechanism	ADP + H2O → AMP + PPi	ATP + H2O → ADP + Pi
Functions	Crucial to the flow of energy in living beings Plays a role in catabolic pathways such as citric acid cycle, oxidative phosphorylation, and glycolysis Activation of blood platelets to initiate healing of a broken blood vessel Plays a key role in mitochondrial ATP synthase complex	Main energy carrier molecule in living beings Metabolism in cells Active transportation of molecules Plays a role in cell signaling Activation of amino acid Helps maintain cell structure Synthesis of macromolecules such as DNA, RNA, and proteins

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