Question

What is a nucleic acid monomer and polymer?

Answer 1

Hint: The monomer can be described as a nucleotide composed of three subunits : nitrogen base, the phosphate group and the sugar part. On the other hand, polymers on the basis of types of nucleotides present can be classified as either a RNA or DNA molecule.

Complete answer:
A monomer can be defined as a type of molecule that possesses the ability to chemically bond with other molecules in a long chain. Monomers are defined as building blocks of polymers. Polymers can be described as chains of repeating monomeric units connected with each other by covalent bonds. In case of nucleic acids, monomers are the nucleotides composed of nitrogenous base, pentose sugar, and phosphate group whereas DNA and RNA are considered as polymer of nucleic acids.
DNA and RNA are composed of monomers termed as nucleotides. The nucleotides combine with each other in order to form a polynucleotide which can be either DNA or RNA. Each nucleotide comprises three components: a nitrogenous base, a pentose (five-carbon) sugar and a phosphate group. In a nucleotide each nitrogenous base can be observed to be attached to a sugar molecule which is attached to one or more phosphate groups.
DNA is composed of nucleotides that are single monomeric units. Each nucleotide contains three elements i.e. sugar, nitrogenous base and phosphate group. Sugar (deoxyribose sugar) in DNA is surrounded on one side to a phosphate group and surrounded on the other side to a nitrogenous base.A nucleotide that does not consist of phosphate group is termed as nucleoside. There are two groups of nitrogen bases termed as purines and pyrimidines. The four bases in DNA's alphabet are:adenine (A) - a purine, cytosine(C) - a pyrimidine, guanine (G) - a purine and thymine (T) - a pyrimidine. The nucleotide is formed by glycosidic bond between nitrogenous base and sugar and Ester bond between phosphate group and sugar. Each nucleotide is bounded by a phosphodiester bond to form a polynucleotide chain. The two polynucleotide chains are held together by hydrogen bonds between nitrogenous bases to form double stranded DNA which are weaker in nature. The nitrogenous bases on the two strands of DNA pair up, purine with pyrimidine (A with T, G with C). Between adenine and thymine two hydrogen bonds are present and between guanine and cytosine three hydrogen bonds are present.

Note :
In the case of Lipids, monomers are glycerol and fatty acids and polymers are termed as diglycerides, triglycerides. In the case of Proteins, monomers are amino acids and polymers are termed as polypeptides. In the case of Carbohydrates monomers are monosaccharides (simple sugar) and polymers are termed as polysaccharides and disaccharides.