How many of the following can be explained on the basis of osmosis?
(i) A raw mango placed in a concentrated salt solution shrivels.
(ii) A carrot that has become limp becomes firm again when placed in water.
(iii) Scuba divers suffer from bends when they come up towards the surface.
(iv) People taking a lot of salty food show puffiness or swelling of tissues.
(v) Climbers at high altitudes suffer from anoxia.
(vi) A bacterium on salted meat loses water, shrivels and dies.
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 4
Osmosis is the flow of solvent (water) through a semipermeable membrane from the more dilute side to the more concentrated side. Cases where water moves into or out of cells or tissues come under osmosis; cases where a gas dissolves more or less in blood come under Henry’s law.
Explained by osmosis:
(i) Mango in salt solution (loses water to the salt solution)
(ii) Limp carrot in water (water moves into its cells)
(iv) Swelling from salty food (edema) (water retained in tissue cells)
(vi) Bacterium on salted meat (loses water to the salt)
Not explained by osmosis:
(iii) Bends in scuba divers — Henry’s law; as the pressure falls, dissolved nitrogen comes out of the blood as bubbles.
(v) Anoxia in climbers — Henry’s law; the low partial pressure of oxygen gives low oxygen in the blood.
Explained by osmosis: 4 cases.
NCERT (2026-27 edition):
1.6.4 Osmosis and Osmotic Pressure – “…A raw mango placed in concentrated salt solution loses water via osmosis and shrivel into pickle. Wilted flowers revive when placed in fresh water. A carrot that has become limp because of water loss into the atmosphere can be placed into the water making it firm once again. Water will move into its cells through osmosis. … People taking a lot of salt or salty food experience water retention in tissue cells and intercellular spaces because of osmosis. The resulting puffiness or swelling is called edema. … Through the process of osmosis, a bacterium on salted meat or candid fruit loses water, shrivels and dies.”
1.3.2 Solubility of a Gas in a Liquid – “Henry’s law finds several applications in industry and explains some biological phenomena.” … “When the divers come towards surface, the pressure gradually decreases. This releases the dissolved gases and leads to the formation of bubbles of nitrogen in the blood. This blocks capillaries and creates a medical condition known as bends…” … “At high altitudes the partial pressure of oxygen is less than that at the ground level. This leads to low concentrations of oxygen in the blood and tissues … a condition known as anoxia.”