Final answer:
To attach a nucleotide in RNA, two bonds are broken in the incoming nucleotide triphosphate (NTP); the bond between the two phosphates (pyrophosphate) and through a dehydration reaction involving the 3' carbon of the existing chain and the 5' phosphate of the incoming nucleotide.
Step-by-step explanation:
When attaching a nucleotide in RNA, several steps occur that involve breaking and forming bonds. During the polymerization process, a high-energy bond from the incoming nucleotide triphosphate (NTP) is broken. Specifically, the bond between the two phosphates (pyrophosphate) is broken and this is what drives the polymerization process making it energetically favorable. The actual number of bonds broken to attach a nucleotide in RNA is two, as one bond is broken between the phosphates of the NTP, and the other is a dehydration reaction where a hydroxyl group is removed from the 3' carbon of one nucleotide and a hydrogen atom is removed from the hydroxyl group of the 5' phosphate.
The polymerase enzyme facilitates the addition by breaking these bonds to release the needed energy and form the phosphodiester bond between the 3' end of the growing RNA chain and the 5' phosphate of the incoming nucleotide. As phosphodiester bonds are formed, this results in the elongation of the RNA molecule.