What is ATP and why do we need it?

ATP is short for adenosine triphosphate, and it can be thought of as the energy 'currency' in our cells. It has a similar structure to that of an RNA nucleotide, as it is comprised of a nitrogenous base (adenine) and a pentose sugar (ribose). However, ATP has three phosphate groups attached to it opposed to just the one that is present in nucleotide molecules. Hydrolysis (splitting with water) of the ATP molecule splits the bond between two of the phosphate groups, forming ADP (adenosine diphosphate) and a phosphate group (Pi). The phosphate to phosphate bond that is broken is a high energy bond, so it can be used to help give energy to different energy-requiring processes within the cell. Using ATP, opposed to glucose for energy-requiring processes, releases energy in smaller, more manageable amounts. Using all of the energy stored in glucose would otherwise release much more energy than is needed for the vast majority of the processes in our cells.