Question

Phosphorus is present in:
A. Protein
B. DNA
C. RNA
D. Both DNA and RNA

Answer 1

Hint: DNA and RNA are nucleic acids. Nucleic acids have a nitrogenous base, phosphate and Pentose sugar. Nucleic acid was earlier named as nuclein due to its acidic nature.

Complete answer:
Phosphorus is present both in DNA and RNA as it forms the backbone of the nucleic acid. The acidic nature of nucleic acids is due to the presence of phosphoric acid.
Nucleic acid is a macromolecule, made up of many monomeric units, called nucleotides. The Pentose sugar, phosphate and nitrogenous base are collectively called nucleotides. Pentose sugar and nitrogenous bases are called nucleosides. Thus, nucleotide is a phosphoric ester of nucleoside. The relationship is shown below:
Nucleic acid = many nucleotides
Nucleotide = nucleosides + phosphate
Nucleoside = sugar + nitrogenous base
Thus nucleic acid, = phosphate + sugar + nitrogenous base
In both DNA and RNA, the phosphorus which is considered to be the backbone helps in the formation of phosphodiester bonds. Sugar of nucleoside combines with phosphoric acid by a phosphoester bond formed at the 5th or 3rd carbon of sugar.
Chemical composition of DNA and RNA:
DNA: Deoxyribose + nitrogenous base + phosphate
                                   (A, G, C, T)
RNA: Ribose + nitrogenous base + phosphate
                                   (A, G, C, U)

So, the correct answer is option D. ‘both DNA and RNA’.

Note:
Nucleic acid was discovered by Fredrich Miescher.
Phosphorus is the central atom of the phosphate group.
Nitrogenous base in DNA, Adenine, Guanine, Cytosine, Thymine.
Nitrogenous base in RNA, Adenine, Guanine, Cytosine, Uracil.