What is respiration and why is it needed?

Respiration is the process of using energy stored in complex organic molecules (such as carbohydrates, fats and proteins) to make ATP.

ATP (Adenosine Tri-Phosphate) is a molecule and is called the 'universal energy currency of the cell'.

It effectively stores the energy released by respiration and when it is broken down it in turn releases this energy to meet our metabolic needs (ie all the chemical reactions taking place in our cells to drive all the biological processes).

These include:

1) Transport of ions e.g. in neurones for the transmission of impulses particularly against their natural concentration gradient (active transport). 

2) Transport of molecules inside and outside of cells. 

3) DNA synthesis and/or replication.

4) Activating/modifying chemicals e.g. by adding from phosphate groups taken from ATP.

5) Movement both at a cellular level and of the whole organism.