A myelinated axon has a sheath around it and a bore axon doesn't have it, it's open or exposed so to speak. T<span>he myelin is made up of fat and protein and works like insulation. these axons make up the white matter in the brain since it appears white. The sheath helps to keep the electrical current from leaving the axon and the myelin sheath provides a tract along which regrowth can occur. </span>
Purines: Heterocyclic rings are synthesized one atom at a time, first atom attached to ribose phosphate (source is PRPP) and then all the other atoms are added .
Pyrimidines: Common intermediate, orotate, synthesized first, then orotate is attached to ribose phosphate (source is PRPP or 5-Phosphoribosyl-1-pyrophosphate).
