Define the following terms as related to proteins
(i) Primary structure
(ii) Secondary structure
(iii) `beta` - strands

Explanation

(i) Primary structure of proteins :
Proteins are polypeptide chains made up ofamino acids connected through peptide bonds. The relative arrangement of the amino acids in the polypeptide chain is called the primary structure of the protein.
(ii) Secondary structure of proteins :
The amino acids in the polypeptide chain forms highly regular shapes (sub- structures) through the hydrogen bond between the carbonyl oxygen ( -C=O) and the neighbouring amine hydrogen ( - NH) of the main chain.
`beta`-Strands are extended peptide chain rather than coiled. The hydrogen bonds occur between main chain carbonyl group one such strand and the amino group of the adjacent strand resulting in the formation of a sheet like structure. This arrangefi?.ent is called `beta`-sheets.