​Three strands of a beta-sheet of 4 peptides are hydrogen bonded with the orientation of the strands (parallel or antiparallel denoted by the arrowheads) as shown in the figure. Each strand consists of identical residues, where N and C represent terminal residues of the peptide. The three strands of each peptide are linked by amino acid sequences of the smallest length possible.​

​Which one of the following options is correct regarding the length of the peptides 1 to 4?​

Correct option is B

Explanation:
Peptide 1 and Peptide 2 are oriented parallel to each other, while Peptide 3 and Peptide 4 are antiparallel.

​Parallel Beta-sheet (Peptides 1 and 2):

The hydrogen bonds are less favorable because the N-terminus of one strand is aligned with the N-terminus of the adjacent strand. This arrangement is typically less stable and leads to shorter peptide chains.

​Antiparallel Beta-sheet (Peptides 3 and 4):

The hydrogen bonds are more stable because the N-terminus of one strand aligns with the C-terminus of the adjacent strand, making the interactions stronger. This typically leads to longer peptides.

​Peptide 1 is the shortestbecause it is involved in a less stable, parallel arrangement.

​Peptide 2 is the longestbecause it is more stabilized by the parallel arrangement but has a larger sequence involved in hydrogen bonding.

​Peptide 3 and Peptide 4 are similar in lengthbecause they are antiparallel, and the peptide chains are longer than those in the parallel arrangement.

Conclusion:
Peptide 1 < (Peptide 3 = Peptide 4) < Peptide 2.
Correct Answer: Option 2.​