polypeptidejä

Polypeptidejä are long chains of amino acids linked together by peptide bonds. They are the building blocks of proteins. The sequence of amino acids in a polypeptide chain determines its three-dimensional structure and, consequently, its function. Proteins can be composed of a single polypeptide chain or multiple polypeptide chains.

The synthesis of polypeptide chains occurs during translation, a process where ribosomes read the genetic code carried by messenger RNA (mRNA) molecules. Each mRNA molecule carries instructions for a specific polypeptide sequence. Amino acids are brought to the ribosome by transfer RNA (tRNA) molecules, which match specific codons on the mRNA. As the ribosome moves along the mRNA, it catalyzes the formation of peptide bonds between successive amino acids, thus elongating the polypeptide chain.

Once synthesized, a polypeptide chain folds into a specific three-dimensional conformation, which is crucial for its biological activity. This folding process is often assisted by chaperone proteins. The final structure of a protein can range from a simple globular shape to complex quaternary structures formed by the association of multiple polypeptide chains.

Polypeptides are involved in virtually all biological processes, including enzymatic catalysis, structural support, transport, signaling, and immune responses. Their diverse functions are a direct consequence of the vast number of possible amino acid sequences and the intricate ways they fold. Alterations in polypeptide sequences, due to genetic mutations, can lead to dysfunctional proteins and diseases.