The structure of a nucleotide and the formation of nucleic acid chains. As shown in the inset, a nucleotide is composed of a five carbon sugar, a phosphate group, and an organic nitrogen base. The sugar and phosphate groups make up the back bone of a nucleic adic chain, while the nitrogenous bases link the two sides of the chain. A five-carbon sugar 2. The order in which the nucleotides are linked together forms a code that ultimately specifies the order of amino acids in a particular protein.
Organisms have two forms of nucleic acid.