Each carbon atom in the pentose sugar is
   assigned a number with a prime sign (').

   Ribonucleic acids (RNA) contain ribose, a 5-carbon sugar.

   Deoxyribonucleic acids (DNA) contain deoxyribose, which has a hydrogen
   atom at the 2' carbon rather than a hydroxyl group.

   A  ribose  or  deoxyribose  sugar  with  a  purine  or pyrimidine base
   attached to the 1' carbon is called a nucleoside.