Question

What is meant by the secondary structure of proteins?

Answer 1

A protein is a highly complex natural product made up of amino acid residues linked by peptide bonds. Proteins are found in all living organisms and contain a variety of biologically important substances such as enzymes, hormones, and antibodies.

Complete answer:
PROTEIN SECONDARY STRUCTURE: This depends on the polypeptide backbone's normal folding patterns. Polypeptide chains are stabilised in one of two patterns: $\alpha$-helix or $\beta$-sheet.
$\alpha$-helix
The R groups of the amino acid residues protrude outward from the helical backbone, and the polypeptide backbone is closely bound along an imaginary axis traced longitudinally along the centre of the helix. There are 3.6 amino acid residues in each helical turn. The right-handed helical twist of the $\alpha$ -helix present in both proteins. Internal hydrogen bonds are used to their full potential in an $\alpha$ helix.
$\beta$-sheet
Polypeptide chains are arranged into sheets using the $\beta$ -conformation. The backbone of the polypeptide chain is extended into a zigzag configuration rather than a helical structure in the beta- conformation. The zigzag polypeptide chains can be stacked on top of each other to form a pleated shape. Hydrogen bonds are formed between adjacent segments of the polypeptide chain in this configuration, known as a $\beta$ -sheet. The alternating pattern is generated by the R groups of neighbouring amino acids protruding in opposite directions from the zigzag arrangement. A $\beta$ -neighboring sheet's polypeptide chains may be parallel or antiparallel.

Note:
A protein is a highly complex natural product made up of amino acid residues linked by peptide bonds. Proteins are found in all living organisms and contain a variety of biologically important substances such as enzymes, hormones, and antibodies.