Skip to content
ICSE Question Bank
2023Q8(iv)Absorption by Roots – The Processes Involved
DefinitionModerate2 marks

What is the semi permeable membrane? Name the semi permeable membrane present in a plant cell.

Topic: Semi-permeable membrane

Previous-year question practice database

Answer

Exam answer

A SEMI-PERMEABLE (selectively permeable) MEMBRANE is one that allows only CERTAIN molecules — chiefly the solvent, water — to pass through it, while holding back others such as the dissolved solute.

In a plant cell the semi-permeable membrane is the PLASMA MEMBRANE (cell membrane).

Explanation

One mark for the definition and one for naming the membrane, so do not omit either.

THE DISTINCTION THAT MATTERS, and it is examined repeatedly: in a plant cell it is the PLASMA MEMBRANE that is selectively permeable, NOT the cell wall. The CELL WALL is FREELY PERMEABLE — it lets everything through, solutes included.

That is why, in a plasmolysed cell, the gap between the shrunken protoplasm and the wall is filled with the external HYPERTONIC SOLUTION: the solution passed straight through the wall and was stopped only at the plasma membrane. The 2025 paper asks you to label exactly that.

Semi-permeability is what makes OSMOSIS possible: without it, solute and solvent would simply diffuse and no osmotic pressure could arise.

More from Absorption by Roots – The Processes Involved

Varun’s mother added plenty of salt to the mango pickle she made. This is to: A. enhance the colour of the pickle. B. inhibit the growth of microorganisms. C. increase the nutritional value. D. create a hypertonic solution.2026Differentiate between Plasmolysis and Deplasmolysis.2026Write the term for the pressure exerted by the cell contents on the cell wall.2026Given below is the diagram of a turgid plant cell. Copy the diagram and label Vacuole and Plasma membrane.2026Assertion (A): A turgid plant cell is in a balanced state. Reason (R): In a turgid cell, turgor pressure and wall pressure are equal and in the same direction.2025Given below is the diagram of a plasmolysed cortical cell of a root. Copy the diagram and label the following parts: (a) Cytoplasm (b) Hypertonic solution (c) Plasma membrane2025