After cutting cucumber if salt is added, then water comes out due to

Question

UnlockIAS · Accepted Answer

Correct — C, Osmosis. When salt is sprinkled on cut cucumber, it dissolves in the surface film of water and creates a region of high solute concentration (low water potential) OUTSIDE the cucumber cells. The water inside the cells has a higher water potential, so it moves out across the selectively (semi-)permeable cell membranes towards the salty, more concentrated exterior. This net movement of the solvent (water) across a semipermeable membrane from higher to lower water potential is osmosis — which is why water oozes out of the salted cucumber (the cells lose turgor and plasmolyse).

Why the other options are wrong — (a) Wrong — active transport moves solute particles AGAINST their concentration gradient and needs energy (ATP) and carrier proteins. Here it is water, not a solute, that moves, and it moves passively down its water-potential gradient with no energy spent.  (b) Not the specific term. Passive transport is a broad umbrella (diffusion, facilitated diffusion and osmosis) for movement down a gradient without energy. Osmosis IS a kind of passive transport, but the question asks for the precise process by which water crosses the membrane — that exact term is osmosis, so (c) is the expected answer.  (d) Wrong — diffusion is the general net movement of any particles from higher to lower concentration. When the moving substance is specifically water crossing a semipermeable membrane, the process is given the special name osmosis; the outflow of water here is osmosis, not ordinary diffusion.

Concept: Osmosis is the net movement of solvent (water) molecules across a selectively permeable membrane from a solution of higher water potential (more dilute) to one of lower water potential (more concentrated), until equilibrium. Cell membranes are semipermeable, so cells lose water by osmosis in a hypertonic (saltier) surrounding and gain water in a hypotonic one. Sprinkling salt makes the cucumber's surroundings hypertonic, so its cells lose water and plasmolyse.

State PCS 2021 Q77 — Science & Technology PYQ with Answer

State PCS 2021 Q77 — Science & Technology PYQ with Answer