The three units that make up a nucleotide are phosphates, a five-carbon sugar and a nucleotide base. Five nucleotide bases make up nucleotides: adenine, thymine, guanine, cytosine and uracil.
Nucleotides are the building blocks of the nucleic acids, namely, deoxyribonucleic acid, or DNA, and ribonucleic acid, or RNA. Three phosphate groups, either deoxyribose or ribose sugar and one of the nucleotide bases make up a nucleotide; however, when nucleotides come together to form nucleic acids, two of the phosphate groups are cut off, leaving a single phosphate group. A phosphate group is made up of a single phosphorus atom bound to oxygen atoms.
The phosphate group is bonded to the sugar, and the sugar is bonded to the nucleotide base. RNA consists of the bases adenine, uracil, guanine and cytosine; DNA contains the bases adenine, thymine, guanine and cytosine.