Osmosis

noun (uncountable)

/ɒzˈməʊsɪs/

Osmosis is the passive movement of water molecules across a selectively permeable membrane from a region of lower solute concentration (higher water potential) to a region of higher solute concentration (lower water potential), until equilibrium is reached. In biological systems, it governs cell turgor, renal water reabsorption, and the absorption of water by plant roots from the soil. In Indian agriculture, osmotic stress from saline soils critically reduces crop yields in states like Rajasthan and the Indus-Gangetic plain.

✍️ Usage in a UPSC answer

The process of osmosis underpins renal water reabsorption in the loop of Henle, a mechanism directly relevant to understanding kidney disease burdens that affect over 17% of India's adult population.

Synonyms

diffusion (of water)endosmosisexosmosispassive transportmembrane filtration

Antonyms

active transportplasmolysis (reverse osmosis effect)exosmosis

🌱 Word Family

osmotic (adjective), osmotically (adverb), osmoregulation (noun), osmoregulate (verb)

🔡 Root

Greek ōsmos = push, thrust; from ōthein = to push

📜 Etymology

Derived from Modern Latin osmosis, coined in the mid-19th century from Greek ōsmos (a push or thrust), itself from ōthein (to push). The Scottish chemist Thomas Graham first described the principle in 1854, and the term was formalised by Wilhelm Pfeffer in 1877. The word entered biological and chemical science to describe the directional movement driven by concentration gradients.

🧠 Memory Hook

Think of osmosis as water being 'pushed' (Greek ōthein = push) toward the crowd — water always moves toward where solutes are denser, just as crowds draw more people in. Picture a crowd of salt molecules pulling water molecules across a membrane barrier.

⚗️ General Science 📖 Seen in: Human Body Systems — Organ Systems, Ph...

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