What is the primary building block of proteins?

The primary building block of proteins is amino acids. Proteins are large biomolecules that play critical roles in the body, including serving as enzymes, structural components, and signaling molecules. They are composed of long chains of amino acids, which are linked together through peptide bonds. The sequence and composition of these amino acids determine the structure and function of each specific protein.

Amino acids themselves consist of a central carbon atom bonded to an amino group, a carboxyl group, a hydrogen atom, and a variable side chain (R group) that differs among amino acids. There are 20 standard amino acids used by living organisms, and their unique combinations form the great diversity of proteins found in nature.

The other options represent different types of biological molecules that are not involved in protein synthesis. Fatty acids are the building blocks of lipids (fats), while sugars are the monomers that form carbohydrates. Nucleotides are the basic units of nucleic acids, such as DNA and RNA. Thus, while these molecules are essential for various biological functions, amino acids are specifically the fundamental components that make up proteins.