Q.Proteins perform many physiological functions. For example some functions as enzymes. One of the following represents an additional function that some proteins discharge:

Step 1. Note what the question needs. It asks for a genuine ADDITIONAL protein function, distinct from the enzyme role already given, so each option must be checked for whether it is actually built from protein.

Step 2. Check option (a) Antibiotics. Most antibiotics are small non-protein secondary metabolites (a few natural antibiotics are peptides, but 'antibiotic' as a category is not a standard recognised protein function).

Step 3. Check option (b) Pigment conferring colour to skin. Skin pigment is melanin, which is a polymer built from oxidised tyrosine derivatives, not a protein or polypeptide itself - even though the enzyme tyrosinase (a protein) helps synthesise it.

Step 4. Check option (c) Pigments making colours of flowers. Flower pigments are typically anthocyanins and carotenoids, which the chapter itself classes as secondary metabolites/pigments, not proteins. …

Check which option is actually a protein/polypeptide molecule rather than a pig …

• Assuming any biological pigment (skin or flower colour) must be a protein - most are non-protein secondary metabolites (melanin, anthocyanins, caro …