Question

Write a short note on primary and secondary structures of proteins.

Hint:

Remember: Primary = sequence of amino acids, Secondary = hydrogen-bonded folding (alpha-helix, beta-sheet).

Answer 1

Step 1: Primary structure.
- The primary structure of proteins refers to the linear sequence of amino acids in a polypeptide chain, joined by peptide bonds. - This sequence determines the unique characteristics and function of the protein. - Even a single change in the amino acid sequence can alter protein activity (e.g., sickle-cell anemia caused by a single amino acid substitution in hemoglobin). Step 2: Secondary structure.
- The secondary structure refers to the regular folding or coiling of the polypeptide chain due to hydrogen bonding between the C=O and N–H groups of peptide bonds. - Two major forms are: \begin{enumerate} \item
Alpha-helix: Right-handed coiled structure stabilized by intramolecular hydrogen bonds. \item
Beta-pleated sheet: Zig-zag structure where polypeptide chains lie side by side, stabilized by intermolecular hydrogen bonds. \end{enumerate} - These structures provide stability and define the shape of proteins. Conclusion:
The primary structure gives the amino acid sequence, while the secondary structure defines local folding patterns such as alpha-helices and beta-sheets, both crucial for protein function.