Question

A nucleotide consists of
A.Carbon sugar
B.Nitrogen containing base
C.Phosphoric acid
D.All of the above

Answer 1

Hint: A nucleotide has three distinct units. When a phosphate group is attached to a nucleoside, it is known as nucleotide. A nucleotide of DNA is different from a nucleotide of RNA in terms of constituent molecules.

Complete step by step answer:
- Carbohydrate, proteins and nucleic acids comprise the macromolecular fraction of any living tissue or cell. Nucleic acids are the polymers with their monomeric unit as nucleotides. There are two types of nucleic acid depending on the constituents of nucleotides namely DNA deoxyribonucleic acid and RNA ribonucleic acid. A nucleotide consists of 3 subunits namely sugar, nitrogenous base and phosphate group. Sugar in the nucleotide can be either ribose or deoxyribose. Both these are five carbon sugars.
- A nucleotide of DNA has deoxyribose sugar and a nucleotide of RNA has ribose sugar. Nitrogenous base in a nucleotide can be either purine or pyrimidine. Purines are adenine and guanine which consist of two heterocyclic rings. Pyrimidines are cytosine, uracil and thymine which consist of one heterocyclic ring each. DNA can only have any one of them: Adenine, Guanine, Cytosine and Thymine nitrogenous base in each of its nucleotides.
- On the other hand, RNA can only have any one of them: Adenine, Guanine, Cytosine and Uracil nitrogenous base in each of its nucleotides. Phosphate group is present in each nucleotide. Adjacent nucleotides are joined together by phosphodiester bonds which are made between phosphate groups of adjacent nucleotides. Sugar molecules and nitrogenous bases are joined together by glycosidic linkage.
- DNA is double stranded and both the strands are linked together by hydrogen bonds formed between complementary nitrogenous bases. As Adenine binds with Thymine with two hydrogen bonds and on the other hand, Cytosine binds with Guanine with three hydrogen bonds. RNA is a single stranded polymer of nucleotides.

Thus, the correct option is D.

Note:
A nucleotide without phosphate group is known as nucleoside. Thus nucleoside contains sugar molecules and nitrogenous bases. The strands of DNA are antiparallel and complementary to each other.