What is the fundamental unit of proteins?

The fundamental unit of proteins is the amino acid. Proteins are macromolecules composed of long chains of amino acids linked together by peptide bonds. There are 20 different amino acids that can combine in various sequences to form a wide variety of proteins, each with distinct functions in biological systems. This sequence and the properties of the amino acids dictate the structure and function of the resulting protein.

Amino acids consist of a central carbon atom attached to an amino group, a carboxyl group, a hydrogen atom, and a distinctive side chain or R group. The unique properties of the side chains determine the characteristics of each amino acid, influencing how they interact with one another and fold into specific three-dimensional shapes that are crucial for the protein's functionality.

In contrast, nucleotides are the building blocks of nucleic acids like DNA and RNA, sugars are carbohydrates that serve various energy and structural roles within cells, and fatty acids are components of lipids, which are important for energy storage and membrane structure. Therefore, while all these molecules are essential in biological functions, it is the amino acid that specifically serves as the fundamental building block of proteins.