Polypeptidiketjut

Polypeptidiketjut, often referred to in English as "peptide bonds" or "peptide linkages," are covalent chemical bonds formed between two molecules when the carboxyl group of one amino acid reacts with the amino group of another. This reaction results in the formation of an amide bond, releasing a molecule of water in the process—a reaction known as a condensation reaction. Peptide bonds are fundamental to the structure and function of proteins, which are essential macromolecules in living organisms.

The sequence of amino acids in a polypeptide chain is determined by the genetic code and is crucial for the protein’s three-dimensional structure and biological activity. The linear chain of amino acids linked by peptide bonds is called a polypeptide. Polypeptides can vary greatly in length, from short chains of just a few amino acids to very long chains containing hundreds or thousands of amino acids, which are then referred to as proteins.

Peptide bonds exhibit partial double-bond character due to resonance stabilization, which restricts rotation around the bond and contributes to the rigidity of the polypeptide backbone. This rigidity plays a key role in the folding patterns of proteins, such as alpha helices and beta sheets, which are stabilized by hydrogen bonds between adjacent amino acid residues.

In addition to their role in proteins, peptide bonds are also found in smaller peptides, which serve various functions in biological systems, including hormone regulation, immune responses, and neurotransmission. Synthetic peptides are widely used in research, medicine, and biotechnology, often as drugs or diagnostic tools due to their specificity and lower immunogenicity compared to larger proteins.