Nitrogenous Base
Purines and pyrimidines are the two categories of nitrogenous bases. Adenine and guanine are purines. Cytosine, thymine, and uracil are pyrimidines. In DNA, the bases are adenine (A), thymine (T), guanine (G), and cytosine (C). In RNA, the bases are adenine, thymine, uracil, and cytosine,   Pentose Sugar
In DNA, the sugar is 2'-deoxyribose. In RNA, the sugar is ribose. Both ribose and deoxyribose are 5-csrbon sugars. The carbons are numbered sequentially, to help keep track of where groups are attached. The only difference between them is that 2'-deoxyribose has one less oxygen atom attached to the second carbon.   Phosphate Group
A single phosphate group is PO43-. The phosphorus atom is the central atom. One atom of oxygen is connected to the 5-carbon in the sugar and to the phosphorus atom. When phosphate groups link together to form chains, as in ATP (adenosine triphosphate), the link looks like O-P-O-P-O-P-O, with two additional oxygen atom attached to each phosphorus, one on either side of the atom.
(Just copied from someone's Blog)

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