Final answer:
In DNA and RNA, the nitrogenous bases are adenine, guanine, cytosine, and thymine (only in DNA) or uracil (only in RNA). Purines, like adenine and guanine, have two carbon-nitrogen rings, while pyrimidines, like cytosine, thymine, and uracil, have one. Nucleosides are sugar and base only, while nucleotides also include phosphate groups.
Step-by-step explanation:
In both DNA and RNA, the building blocks known as nucleotides consist of three parts: a sugar, a phosphate group, and a nitrogenous base. Adenine (A) and guanine (G) are the purines, which have a double-ring structure. Cytosine (C), thymine (T), and uracil (U) are the pyrimidines, which have a single-ring structure. In DNA, the nitrogenous bases are A, T, G, and C, while in RNA, uracil (U) replaces thymine (T).
Purines differ from pyrimidines in that purines have a two-ringed structure while pyrimidines have a single ring. This makes purines larger and more complex in shape compared to the smaller pyrimidines. Each base differs in its structure due to the presence of different functional groups that attach to the carbon-nitrogen ring(s), giving them unique properties and allowing for complementary base pairing—A with T (or U in RNA) and G with C—in DNA and RNA leased consists of only a sugar and a nitrogenous base, whereas a nucleotide is a nucleoside with one or more phosphate groups attached.