Nucleic acids are composed of nucleotide monomers, which consist of a nitrogenous base, a pentose sugar, and a phosphate group. As the names suggest, the sugar found in RNA (Ribonucleic acid) is a pentose sugar called ribose, while the sugar found in DNA (Deoxyribonucleic acid) is 2'-deoxyribose . The difference between them is the presence of an -OH group at the 2' carbon in ribose, which is replaced by just an -H atom in 2'-deoxyribose.