Adenosine Triphosphate (ATP) is a chemical that all cells use to
allow reactions to take place. ATP is the "energy currency" of the cell.
The ATP molecule has five components. A chemical called adenine also used
in the cell as a DNA nucleotide (sub-unit of DNA) is attached to a sugar.
Together they are called adenosine. The adenosine is connected then to
three phosphate groups. That is where the "Tri" in triphosphate comes
from. The ATP molecule is very reactive. So much so that it
willingly gives off energy in a reaction. When it gives energy to a
reaction one of the phosphate groups fall off. This changes the ATP to ADP
(adenosine diphosphate). An enzyme is needed for this to take place, but
it releases a great deal of energy each time. This is the ultimate form of
energy for the cell. All cellular process require the use of ATP to drive
ATP is produced in the mitochondria on a phospholipid membrane called the cristae. When glucose is broken down through a process called cellular respiration, ADP is converted to ATP by sticking a phosphate back on to the ADP. When the Phosphate group is added back to the ADP energy has to be added to make it stick. That very same energy is given away (used) in a reaction when ATP is changed to ADP. This is how the reaction is written:
ADP + P + Energy
ADP + P + Energy ATP
ATP is made when glucose is metabolized and broken down into
carbon dioxide and water. The bonds that made up the glucose are then used
to place the phosphates back on ADP.