Final answer:
The ß-pleated sheet is a secondary structure in proteins where polypeptide chains align side by side, held together by hydrogen bonds, forming a sheetlike appearance with side chains extending above and below.
Step-by-step explanation:
The ß-pleated sheet is a common type of secondary structure found in proteins. This structure involves portions of polypeptide chains aligning side by side in either parallel or antiparallel fashion. The chains are then held together by hydrogen bonds between the carbonyl groups of one amino acid and the amine groups of another.
This creates a sheetlike arrangement where the side chains of the amino acids protrude from the sheet, alternating above and below it. ß-Pleated sheets are particularly prominent in structural proteins, like silk fibroin, and can also be found in enzymes such as carboxypeptidase A and lysozyme.
The formation and stability of ß-pleated sheets are influenced by the specific amino acids present, as certain residues have higher propensities for forming this structure. Notably, in the ß-pleated sheet structure, the polypeptide chains are visually represented as ribbons with an arrowhead pointing toward the N-terminus.