Question

what is the monomer building block of proteins? polypeptide amino acid nucleotide carbohydrate

Explanation:

To determine the monomer (building block) of proteins, we analyze each option:

• Polypeptide: A chain of amino acids, not a monomer.
• Amino acid: Proteins are polymers made by linking amino acids via peptide bonds, so amino acids are the monomers.
• Nucleotide: Monomer of nucleic acids (DNA/RNA), not proteins.
• Carbohydrate: Monomers like monosaccharides (e.g., glucose) for carbs, not proteins.
• (Assumed "Fatty acid" or similar, but fatty acids are part of lipids, not protein monomers).

Answer:

B. Amino acid (assuming the second option is labeled B; if the original had labels like A - E, adjust, but based on the options, the correct one is Amino acid as the monomer of proteins)