The building blocks of proteins and enzymes are molecules formed by carboxyl acids attached to amino groups (-NH₂), known as amino acids. Most protein structures consist of combinations of only about twenty of the most commonly found amino acids.

Amino acids bind to each other to form peptides and proteins. Conventionally, the term protein is used to designate chains of several peptides, known as polypeptides, with a molecular weight higher than thousands of Daltons. Peptides with a biological function go in length from dipeptides and tripeptides, up to polymers with thousands of Daltons.

Most proteins have well-defined structures and their specific biological functions depend upon the correct conformation of the molecular structure. For instance, the majority of soluble proteins of an organism, such as blood proteins, have globular structures, like small eggs. Some proteins are fiber-like and are associated in bundles, forming fibrils such...