Write one difference between $\alpha $-helix and $\beta $-pleated structures of proteins.

Hint: This question gives the knowledge about secondary structures of proteins. Secondary structures of proteins consist of various polypeptide chains. The shape of the structures are in such a way that they can afford long polypeptide chains.

Complete step by step answer:
The difference between $\alpha $-helix pleated structure and $\beta $-pleated structure is as follows:
$\alpha $-helix pleated structure: These structures attains coil shape. This structure is right handed in which polypeptide chains are coiled up using hydrogen bonding to form $\alpha $-helix pleated structure. Example of $\alpha $-helix pleated structure is keratin.
$\beta $-pleated structure: These structures attains stretched sheets. This structure is left handed in which polypeptide chains are linked together using intermolecular hydrogen bonding to form $\beta $-pleated structure. Example of a $\beta $-pleated structure is silk.

Additional information: Secondary structures of proteins consist of various polypeptide chains. There are two types of secondary structure of proteins, one is $\alpha $-helix pleated structure and the other is $\beta $-pleated structure.
Characteristics of secondary structures of proteins are as follows:
$1$. Polypeptide chains which are present in secondary structures of proteins do not exist in simpler forms.
$2$. The shape of the structures are in such a way that they can afford long polypeptide chains.
$3$. Polypeptide chains experience folds because of the interactions between the carboxyl group and the amino group of the peptide linkage.
$4$. Two types of secondary structure of proteins, one is $\alpha $-helix pleated structure and the other is $\beta $-pleated structure.
$5$. In polypeptide chains, the carbonyl group and amino group of other chains are linked together by hydrogen bonding.
$6$. The local folds which are present in the segments of protein are known as secondary elements which leads to the formation of secondary structure of proteins.

Note: Always remember that secondary structures of proteins consist of various polypeptide chains. And these polypeptide chains do not exist in simpler forms. In polypeptide chains, the carbonyl group and amino group of other chains are linked together by hydrogen bonding.