Assertion (A): Mycorrhizae are symbiotic associations between fungi and plant roots. Reason (R): The fungus provides water and minerals to the plant and receives sugars in return. MCQ with Answer and Explanation

Explanation:
Tetracycline binds to the 30S ribosomal subunit, blocking attachment of aminoacyl-tRNA, thus inhibiting protein synthesis. Penicillin and cephalosporins inhibit cell wall synthesis, vancomycin also inhibits cell wall synthesis. Aminoglycosides like streptomycin also target 30S. Protein synthesis inhibitors exploit the difference between bacterial and human ribosomes.

Explanation:
Robert Hooke observed thin slices of cork under a microscope he designed and saw honeycomb-like compartments which he termed 'cells' in his 1665 book 'Micrographia'. Leeuwenhoek discovered living cells (bacteria, protozoa). Brown discovered the nucleus (1831), and Virchow proposed that all cells arise from pre-existing cells (1855). Hooke's cells were dead, empty cell walls of cork.

Explanation:
Vitamin A is essential for the synthesis of rhodopsin. Deficiency leads to impaired dark adaptation (night blindness) and eventually xerophthalmia. Beri-beri is B₁ deficiency, pellagra B₃, scurvy vitamin C.