The ATP (adenosine triphosphate) molecule has 3 main parts:
- the base adenine - a double ring like section with several nitrogen atoms (blue),
- the 5 carbon sugar ribose in the centre, and
- 3 phosphate groups - a row of phosphorus atoms (orange) surrounded by oxygens (red). These carry negative charges, resulting from the release of H+ from -OH groups around the phosphorus atoms.
can be converted into ADP
(adenosine diphosphate) + Pi (inorganic phosphate), with the release of energy. This is reversible, and ATP
can be reformed.
Similarly, ATP can lose 2 phosphates (pyrophosphate PPi), or ADP can be converted into AMP
(adenosine monophosphate) + Pi (inorganic phosphate), with the release of energy. AMP is an RNA nucleotide, and it can be converted into a DNA nucleotide. AMP can undergo molecular changes and form cyclic AMP which is used in cellular signalling as a "second messenger".