Antibiotics are the chemicals obtained from the useful micro-organisms and employed to kill some harmful micro organisms. But all the antibiotics do not have medicinal importance. Answer the following questions related to antibiotics:
(i) List the properties of the antibiotics to be used in medicines.
(ii) Discovery of penicillin is said to be a serendipity. Why is it called so?
(iii) Name the source of streptomycin antibiotic.