A labelling of the parts of the nucleotide is shown in the image attached.
The building block of DNA and RNA, a nucleotide, is made up of three essential parts. First, through phosphoester linkages, the phosphate group forms the backbone and contributes a negative charge. Second, the pentose sugar—either ribose or deoxyribose—provides the structural support and connects the nitrogenous base and phosphate group.
Last but not least, the nitrogenous base that forms the hydrogen-bonded rungs of the DNA or RNA ladder is categorized as a pyrimidine (cytosine, thymine in DNA), or a purine (adenine, guanine).