The scientist who proposed the 'lock and key' model was: MCQ with Answer and Explanation

Explanation:
Adrenaline (epinephrine) from the adrenal medulla mediates the 'fight-or-flight' response, increasing heart rate, contractility, and blood pressure. Acetylcholine slows heart, insulin lowers glucose, melatonin induces sleep.

Explanation:
Cytokinins are plant hormones that promote cell division, delay senescence by preventing chlorophyll degradation, and stimulate nutrient mobilization. Ethylene promotes ripening and senescence, abscisic acid promotes abscission and dormancy, auxin is involved in cell elongation. Cytokinins are synthesized in roots and transported upward. They are used to prolong the shelf life of leafy vegetables.

Explanation:
Sclerenchyma provides strength, with thick lignified walls; cells are usually dead at maturity. Xylem transports water, phloem transports food, collenchyma is living with uneven thickening.