State the functions of the following:
Cell wall:
Topic: Cell wall
Try it
Pick an option and check your answer. The full worked answer is below either way.
Answer
(c) Gives rigidity and shape to plant cells.
The CELL WALL is a rigid non-living layer of CELLULOSE outside the plasma membrane. It gives the plant cell its RIGIDITY, its definite SHAPE, and protection.
Options (b) and (d) can be struck out at once — ANIMAL cells have no cell wall at all.
OPTION (a) IS THE REAL TRAP, and it tests a distinction examined repeatedly: the cell wall does NOT regulate what enters. It is FREELY PERMEABLE and lets everything through. It is the PLASMA MEMBRANE that is SELECTIVELY PERMEABLE and controls entry.
That is exactly 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 membrane.
It is also why a plant cell can sit in pure water without bursting: the rigid wall pushes back as the cell swells.
Gives rigidity and shape to plant cells.