ATP, ADP and biological energy

ATP - Adenosine Triphosphate
ADP - Adenosine Diphosphate

ATP can be used to store energy for future reactions or be withdrawn to pay for reactions when energy is required by the cell. Animals store the energy obtained from the breakdown of food as ATP.

Adenosine triphosphate is composed of the nitrogenous base adenine, the five-carbon sugar ribose, and three phosphate groups. These three phosphate groups are linked to one another by two high-energy bonds called phosphoanhydride bonds. When one phosphate group is removed by breaking a phosphoanhydride bond in a process called hydrolysis, energy is released, and ATP is converted to adenosine diphosphate (ADP). The energy can be harnessed for cellular work.

When the cell has extra energy (gained from breaking down food that has been consumed or, in the case of plants, made via photosynthesis), it stores that energy by reattaching a free phosphate molecule to ADP, turning it back into ATP.

Energy is stored in the covalent bonds between phosphates, with the greatest amount of energy (approximately 7 kcal/mole) in the bond between the second and third phosphate groups. This covalent bond is known as a pyrophosphate bond.

The energy released from the hydrolysis of ATP into ADP is used to perform cellular work, usually by coupling the exergonic reaction of ATP hydrolysis with endergonic reactions.

Sodium-potassium pumps use the energy derived from exergonic ATP hydrolysis to pump sodium and potassium ions across the cell membrane while phosphorylation drives the endergonic reaction.
ATP, ADP and biological energy

ATP - Adenosine Triphosphate 

What is adenosine triphosphate?

The energy released from food during respiration is used to create molecules of a chemical called adenosine triphosphate or ATP. It is a nucleotide identical to the molecule found in RNA.

ATP is a temporary store of energy, which can be released whenever required for a wide variety of jobs, such as contraction of muscle or synthesis of complex chemicals, such as synthesis of amino acids, protein synthesis, and active transport systems

It is uniquely situated in the middle of the standard of the energy of hydrolysis for phosphate compounds.

Usually only the outer phosphate is removed from ATP to yield energy; when ATP is hydrolyzed, a molecule of adenosine diphosphate (ADP) and one of inorganic phosphate ion are formed and energy is liberated.

ATP is able to power cellular processes by transferring a phosphate group to another molecule (a process called phosphorylation).

This ADP is used to make more ATP and the process repeats itself over and over again.
What is adenosine triphosphate?