Polypeptide chains are made up of monomers called amino acids. These amino acids are organic compounds that contain both an amino group (-NH2) and a carboxyl group (-COOH). There are 20 standard amino acids that are commonly found in proteins.
Each amino acid has a central carbon atom, known as the alpha carbon, which is bonded to four different groups: a hydrogen atom, an amino group, a carboxyl group, and a unique side chain (R group). The side chain varies among different amino acids and determines their specific properties.
When amino acids join together to form a polypeptide chain, they do so through a dehydration synthesis reaction. In this process, the carboxyl group of one amino acid reacts with the amino group of another, releasing a molecule of water and forming a peptide bond. This bond links the amino acids together in a specific sequence, which is determined by the genetic code.
The sequence of amino acids in a polypeptide chain is crucial because it dictates the chain’s folding and, ultimately, the function of the protein. The unique sequence and structure of each protein allow it to perform specific roles in the cell, such as catalyzing biochemical reactions, providing structural support, or facilitating communication between cells.