polypeptíðs

Polypeptides are long chains of amino acids linked together by peptide bonds. They are formed during protein synthesis within living organisms. A polypeptide chain is the fundamental structure of a protein. The sequence of amino acids in a polypeptide determines its unique three-dimensional shape and ultimately its function.

Amino acids are the building blocks of polypeptides. Each amino acid has a central carbon atom, an amino group, a carboxyl group, and a side chain (R-group) that varies among the 20 common types. When two amino acids join, the carboxyl group of one reacts with the amino group of the other, forming a peptide bond and releasing a water molecule. This process, known as dehydration synthesis, repeats to create a long polypeptide chain.

The order of amino acids in a polypeptide is specified by the genetic code carried in DNA. This sequence is known as the primary structure. As the polypeptide chain is synthesized, it begins to fold into more complex structures. The secondary structure involves localized folding, such as alpha-helices and beta-pleated sheets, stabilized by hydrogen bonds. The tertiary structure refers to the overall three-dimensional shape of a single polypeptide chain, influenced by interactions between amino acid side chains. Some proteins consist of multiple polypeptide chains, and their arrangement constitutes the quaternary structure.

Polypeptides are crucial for virtually all biological processes. They form enzymes that catalyze biochemical reactions, structural components of cells and tissues, hormones that regulate bodily functions, and antibodies that defend against pathogens. The specific sequence and folding of a polypeptide are essential for its biological activity, and any alterations can lead to loss of function or disease.