In biochemistry, nucleic acids such as DNA and RNA are long chain polymers built from which basic monomer units?

Introduction / Context:
Nucleic acids, mainly deoxyribonucleic acid DNA and ribonucleic acid RNA, store and transmit genetic information in living organisms. Understanding their basic building blocks is one of the first steps in learning biochemistry and molecular biology. This question asks which type of small molecule acts as the repeating monomer unit that links together to form long nucleic acid polymers, something that is tested frequently in general science exams.

Given Data / Assumptions:

• The nucleic acids in question are DNA and RNA.
• We are looking for the specific monomer that repeats along the polymer chain.
• Options include nucleotides, amino acids, proteins, sugars and fatty acids.
• We assume standard textbook definitions of these biomolecules.

Concept / Approach:
A polymer is a large molecule made by joining many smaller repeating units called monomers. In proteins, the monomers are amino acids, but in nucleic acids the monomers are nucleotides. Each nucleotide consists of three components: a nitrogenous base, a pentose sugar either deoxyribose or ribose, and one or more phosphate groups. During polymerisation, these nucleotides join together through phosphodiester bonds between the sugar of one nucleotide and the phosphate of the next, forming a sugar phosphate backbone with bases projecting out, which together create the long DNA or RNA strand.

Step-by-Step Solution:
Step 1: Recall that DNA and RNA are called nucleic acids and are examples of biological polymers. Step 2: Identify the structural units of nucleic acids. Each unit is a nucleotide made of a base, a sugar and a phosphate group. Step 3: Recognise that amino acids are the monomers of proteins, not nucleic acids. Step 4: Understand that proteins themselves are large polymers of amino acids and cannot be monomers for nucleic acids. Step 5: Realise that simple sugars and fatty acids belong mainly to carbohydrate and lipid classes and do not form the backbone of DNA and RNA. Step 6: Conclude that nucleotides are the correct monomer units used to build nucleic acid polymers.

Verification / Alternative check:
Standard diagrams of DNA and RNA in textbooks show individual nucleotides as repeating blocks, often drawn as base sugar phosphate units. In DNA, four types of nucleotides are used based on the bases adenine, thymine, cytosine and guanine. In RNA, uracil replaces thymine. When nucleotides connect, they form long strands that twist into double helices in DNA or single strands in most RNA molecules. There is no step where amino acids or fatty acids are linked into DNA or RNA, which confirms that nucleotides are the correct monomers of nucleic acids.

Why Other Options Are Wrong:
- Amino acids: These are the monomers of proteins and are linked by peptide bonds, not by phosphodiester bonds in nucleic acids.
- Proteins: These are themselves polymers and cannot be the monomer units of nucleic acids.
- Simple sugars: Sugars do form part of each nucleotide, but by themselves they are not the repeating units of the nucleic acid chain.
- Fatty acids: These are building blocks of many lipids and are not structurally related to nucleic acid backbones.

Common Pitfalls:
Students sometimes confuse nucleotides with nucleosides, which are similar but lack the phosphate group, or they mix up the different classes of biological macromolecules and their monomers. A simple way to remember is that nucleic acids are made from nucleotides, proteins from amino acids, polysaccharides from monosaccharides and many fats from fatty acids and glycerol. Keeping these pairs clear helps avoid mistakes in quick multiple choice questions.

Final Answer:
Nucleic acids such as DNA and RNA are polymers of Nucleotides.