what structural differences makes adenine and guanine different from cytosine, thymine, and uracil? (figure 2-24)

Nitrogenous bases have two distinct families known as purines and pyrimidine, nitrogenous are the building blocks or monomer units of the nucleic acids.

The major and significant difference between purines and pyrimidines is the difference in their structures-

The purines are divided into two different bases called adenine and guanine and each of them have a two-ringed structure formed with a 9-membered molecule and 4 nitrogen atoms which makes it a large in size than purines.

The pyrimidines are divided into 3 bases that are cytosine, uracil, and thymine and all these have only one single ring of six members and 2 nitrogen atoms.  These are smaller in size.

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hope that !         : )