Chapter 21, Problem 13A

Interpretation Introduction

Interpretation: Secondary structure of protein known as the pleated sheet needs to be explained. Two examples of material containing proteins secondary structure needs to be determined.

Concept Introduction:

The secondary structure represents simple, repetitive arrangements at the site of adjacent amino acid residues in the polypeptide chain. It is maintained by the hydrogen bonds between the amide hydrogen and carbon dioxide of the peptide spine. The main secondary structures are-helix and ß-structures.

Explanation of Solution

In aß pleated sheet, the two or more sections of the polypeptide chain are lined up next to each other, holding the sheet-like structure together with hydrogen bonds. Hydrogen bonds are formed between the carbon and amino groups of the spine, while the R groups extend above and below the plane of the sheet. The strands of ß pleated sheet may be parallel, pointing in the same direction (meaning their N- and C-terminals are matched), or in opposite directions (i.e. the N-terminus of one strand is placed next to the other C-terminus).

The secondary structure of protein is a three-dimensional form of local segment. The two common secondary structures are alpha helix and beta sheets, but beta twists and omega traps also occur.