* Pyrophosphate (PPi): This is a molecule consisting of two phosphate groups linked together. It is released during the formation of the phosphodiester bond between the phosphate group of one nucleotide and the sugar of another.
* Water (H₂O): This is released during the condensation reaction that links the nucleotide base to the sugar molecule.
Here's a breakdown of the process:
1. Activation: A nucleoside triphosphate (NTP) like ATP, GTP, CTP, or TTP is activated. This involves the breaking of a high-energy bond within the NTP, releasing pyrophosphate (PPi).
2. Attachment: The activated nucleotide, now a nucleoside monophosphate (NMP), is attached to the 3' hydroxyl group of a growing polynucleotide chain. This involves a condensation reaction that releases water (H₂O).
In summary:
* Nucleotide synthesis involves the formation of a phosphodiester bond and a condensation reaction, releasing pyrophosphate (PPi) and water (H₂O), respectively.
Important note: Pyrophosphate (PPi) is further broken down into two inorganic phosphate molecules (Pi) by an enzyme called pyrophosphatase. This reaction is highly favorable and drives the nucleotide synthesis reaction forward.
