Final answer:
The primary structure of a protein is the unique sequence of amino acids in a polypeptide chain. It is determined by protein sequencing methods and is essential for the protein's function as it dictates the protein's three-dimensional structure.
Step-by-step explanation:
Primary Structure of Proteins:
The primary structure of a protein is the unique sequence of amino acids in a polypeptide chain. This sequence is determined by protein sequencing, a process that traces the formation of a polypeptide. The path to the formation of a polypeptide starts with transcription of a gene into mRNA, followed by the translation of this mRNA by ribosomes into a polypeptide chain. The sequence of amino acids is dictated directly by the gene encoding the protein. After the initial synthesis on a ribosome, a polypeptide chain undergoes folding and processing to achieve a biologically active form.
Protein sequencing can involve methodologies such as Edman Degradation, where polypeptides are hydrolyzed stepwise, revealing each amino acid one by one from the N-terminus, which is the end with a free NH2-group. The primary structure is important because it determines the three-dimensional structure of the protein, which in turn affects the protein's function. For example, the pancreatic hormone insulin consists of two polypeptide chains, A and B, linked by disulfide bonds, with the N-terminal amino acid of the A chain being glycine, and the C-terminal amino acid being asparagine.
Protein primary structure is typically represented by the three-letter or one-letter abbreviation of the amino acids, starting from the N-terminus and ending at the C-terminus, like the polypeptide example Gly-His-Lys (GHL).