Final answer:
The structural polarity of a polypeptide chain extends from the N-terminus (amino terminus) to the C-terminus (carboxyl terminus), reflecting the sequence of amino acids from start to end and the directional folding into secondary and tertiary structures.
Step-by-step explanation:
The structural polarity of the polypeptide chain goes from N-terminus (amino terminus) to C-terminus (carboxyl terminus).
The polypeptide chain structure is determined by its primary structure, comprising a specific amino acid sequence that begins with the N-terminus, where the free amino group is located, and ends with the C-terminus, where the free carboxyl group resides. These chains can fold into various secondary structures such as the α-helix or β-pleated sheet, with the α-helix spiraling clockwise from N-terminus to C-terminus, held by hydrogen bonds. The tertiary structure involves additional folding of the protein into its three-dimensional shape, influenced by a variety of interactions, including hydrophobic interactions and disulfide bridges. A quaternary structure occurs when multiple polypeptide chains join to form a functional protein.