Which of the following is the monomer unit of a nucleic acid?

• A. Nucleotide
• B. Fatty acid
• C. Monosaccharide
• D. Amino acid

Answer: (A)

Verified step by step guidance

1. Understand the structure and function of nucleic acids: Nucleic acids, such as DNA and RNA, are macromolecules responsible for storing and transmitting genetic information. Their structure is composed of repeating monomer units.
2. Define the term 'monomer': A monomer is a small molecule that can bind chemically to other molecules to form a polymer. In the case of nucleic acids, the monomer units are specific to their structure and function.
3. Identify the components of a nucleotide: A nucleotide consists of three parts: a phosphate group, a pentose sugar (either ribose in RNA or deoxyribose in DNA), and a nitrogenous base (adenine, guanine, cytosine, thymine, or uracil). These components are essential for the structure of nucleic acids.
4. Compare the given options: Fatty acids are monomers of lipids, monosaccharides are monomers of carbohydrates, and amino acids are monomers of proteins. None of these are involved in the structure of nucleic acids. Nucleotides are the correct monomer units for nucleic acids.
5. Conclude that the correct answer is 'Nucleotide' based on the structural and functional relationship between nucleotides and nucleic acids.