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Question
Explain the terms primary and secondary structure of proteins. What is the difference between α-helix and β-pleated sheet structure of proteins?
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Solution
Primary structure of proteins: Proteins may have one or more polypeptide chains. Each polypeptide in a protein has amino acids linked with each other in a specific sequence and it is this sequence of amino acids that is said to be the primary structure of that protein. Any change in this primary structure i.e., the sequence of amino acids creates a different protein.
Secondary structure of proteins: The secondary structure of protein refers to the shape in which a long polypeptide chain. The secondary can exist. They are found to exist in two different types of structures viz. α-helix and β-pleated sheet structure. These structures arise due to the regular folding of the backbone of the polypeptide chain due to hydrogen bonding between carbonyl group and –NH– groups of the peptide bond. α-Helix is one of the most common ways in which a polypeptide chain forms all possible hydrogen bonds by twisting into a right-handed screw (helix) with the carbonyl and –NH group of each amino acid residue hydrogen-bonded to the (>C = O) of an adjacent turn of the helix. In β-structure all people chains are stretched out to nearly maximum extension and then laid side by side which are held together by intermolecular hydrogen bonds.
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\[\ce{\underset{(Glycine)}{H2N - CH2 - COOH}}\];
\[\begin{array}{cc}
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|\phantom{......}\\
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