Which statement about beta-sheets is true?

Which statement about beta-sheets is true?

• A. Beta-sheets consist of intra-strand hydrogen bonds within a single strand.
• B. Beta-sheets are formed by loops connecting strands.
• C. Beta-sheets consist of inter-strand hydrogen bonds and can be parallel or antiparallel; strands are extended.
• D. Beta-sheets are always random coil and lack hydrogen bonds.

Answer: (C)

Beta-sheets are stabilized by hydrogen bonds between the backbones of neighboring beta-strands that lie side by side in an extended conformation. The strands can orient in the same direction (parallel) or in opposite directions (antiparallel), and the key point is that the hydrogen bonds connect adjacent strands, not within a single strand. This inter-strand bonding, combined with the extended, pleated arrangement of the strands, gives beta-sheets their characteristic stable, sheet-like structure. They are not formed by loops connecting strands, and they are not random coils lacking hydrogen bonds.

Beta-sheets are stabilized by hydrogen bonds between the backbones of neighboring beta-strands that lie side by side in an extended conformation. The strands can orient in the same direction (parallel) or in opposite directions (antiparallel), and the key point is that the hydrogen bonds connect adjacent strands, not within a single strand. This inter-strand bonding, combined with the extended, pleated arrangement of the strands, gives beta-sheets their characteristic stable, sheet-like structure. They are not formed by loops connecting strands, and they are not random coils lacking hydrogen bonds.