Question

In the nucleic acids, the phosphate ions are bonded with sugar at:
A. 5, 3 locations
B. 5, 2 locations
C. 3, 1 locations
D. 5, 1 locations

Answer 1

The monomeric unit i.e. single unit of nucleic acids are known by the name nucleotides. Nucleic acids are basically formed by the chain of nucleotides therefore these are known as polynucleotides. Where poly represents many i.e. many parts of nucleotides.

Complete answer:
Nucleotide is basically composed of three parts consisting of a base that has a nitrogen atom called nitrogenous base, a five carbon sugar and anion of phosphoric acid. Naturally occurring nucleic acids contain two types of pentose sugars called Ribose and Deoxyribose sugar and all these known sugars in nucleic acids have the D-stereo isomeric configuration. Where ribose sugar is found in RNA and deoxyribose sugar is present in DNA.
Sugar and nitrogenous base join with each other to form nucleoside and the bond between sugar and the base is called the glycosidic bond which is free to rotate. In the nucleic acids the phosphate ions are bonded with sugar at 5, 3 locations. The sugars and phosphates in nucleic acids are connected through phosphodiester linkages with each other in an alternating manner in the form of chains. The carbons to which the phosphate groups attach are the 3rd end and the 5th end carbons of the sugars.
Hence, option (A) is the correct answer.

Note: Nucleotide can have one, two or phosphate groups which are known as $\alpha ,\beta \text{ and }\gamma$ for first, second and third phosphate group and bond between the sugar and phosphate is phosphoester bond which is basically a covalent bond.