Which of the following is the monomer unit that makes up proteins?

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

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the concept of a monomer. A monomer is a small molecule that can bind chemically to other molecules to form a polymer. Proteins are polymers, so we need to identify the specific monomer that forms proteins.
2. Step 2: Recall the structure and function of proteins. Proteins are macromolecules that perform various functions in the body, such as catalyzing reactions (enzymes), providing structural support, and facilitating communication between cells.
3. Step 3: Identify the building blocks of proteins. Proteins are made up of chains of amino acids, which are linked together by peptide bonds. Each amino acid contains an amino group (-NH₂), a carboxyl group (-COOH), and a unique side chain (R group).
4. Step 4: Compare the options provided: Amino acid, Nucleotide, Fatty acid, and Monosaccharide. Nucleotides are the monomers of nucleic acids (DNA and RNA), fatty acids are components of lipids, and monosaccharides are the monomers of carbohydrates. Amino acids are the correct monomer for proteins.
5. Step 5: Conclude that the correct answer is 'Amino acid,' as it is the monomer unit that makes up proteins.