Final answer:
The B-pleated sheet can occur in both parallel and antiparallel orientations, with the N-terminals facing the same or different directions. Interchain hydrogen bonding provides mechanical strength to proteins.
Step-by-step explanation:
The B-pleated sheet can occur in both parallel and antiparallel orientations. In the parallel B-pleated sheet, the N-terminals of adjacent chains face the same direction, while in the antiparallel B-pleated sheet, the N-terminals face different directions. The sheets are held together by interchain hydrogen bonding, which gives mechanical strength to proteins.