What is the basic structural unit of proteins?

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

Answer: (B)

The basic structural unit of proteins is the amino acid. Amino acids are organic compounds that consist of a central carbon atom bonded to a carboxyl group, an amino group, a hydrogen atom, and a distinctive side chain (R group) that varies among different amino acids. These side chains are what give each amino acid its unique properties.

Proteins are made up of long chains of amino acids linked together by peptide bonds, which are formed through a condensation reaction where the carboxyl group of one amino acid reacts with the amino group of another, releasing a molecule of water. This sequence and arrangement of amino acids in a protein determine its structure and function, making amino acids the fundamental building blocks of all proteins.

In contrast to other options, nucleotides are the building blocks of nucleic acids like DNA and RNA, fatty acids are components of lipids, and monosaccharides are the simplest form of carbohydrates. Each of these has distinct roles in biological processes, but they do not constitute the structural units for proteins.