Final answer:
A nucleotide is made up of a sugar, a phosphate group, and a nitrogenous base. This structure is essential in the formation of nucleic acids, with the bases adenine (A), cytosine (C), guanine (G), and thymine (T) in DNA, and uracil (U) in RNA replacing thymine.
Step-by-step explanation:
A nucleotide consists of a sugar, a phosphate group, and a nitrogenous base. These small molecules serve as the building blocks of nucleic acids, which include DNA and RNA. Nucleotides are composed of three main components: a 5-carbon sugar (pentose), which is either deoxyribose in DNA or ribose in RNA; one or more phosphate groups; and a nitrogen-containing base, which can be one of five types. In DNA, the nitrogenous bases are adenine (A), cytosine (C), guanine (G), and thymine (T); whereas in RNA, thymine is replaced by uracil (U). The other three bases are present in both DNA and RNA. This structure is essential for the nucleotide's role in forming nucleic acids and other important molecules such as adenosine triphosphate (ATP).