Select the correct answers to the questions from the given options. (Do not copy the questions, write the correct answer only.)
Osmosis takes place when there is:
Topic: Conditions for osmosis
Try it
Pick an option and check your answer. The full worked answer is below either way.
Answer
(c) A selectively permeable membrane.
Osmosis REQUIRES a SELECTIVELY (semi-) permeable membrane — one that lets the SOLVENT (water) pass but holds back the SOLUTE. It is that selectivity which forces water alone to move, from the weaker solution to the stronger.
Test each wrong option against the definition: FREELY PERMEABLE — everything passes, solute included, so the movement would be simple DIFFUSION, not osmosis. This is what a plant CELL WALL is, which also disposes of option (b). IMPERMEABLE — nothing passes at all, so no movement occurs.
In a plant cell it is the PLASMA MEMBRANE, not the cell wall, that is selectively permeable — the distinction tested by the plasmolysis diagram in the 2025 paper.
DEFINITION worth holding: osmosis is the movement of solvent molecules from a region of higher water concentration to one of lower, THROUGH A SELECTIVELY PERMEABLE MEMBRANE.
A selectively permeable membrane.