Q1. Describe the structure of the cell wall and explain how it gives strength to plant cells.
Answer:
The cell wall is a rigid outer layer outside the plasma membrane.
It is mainly made of cellulose fibers.
These fibers form a strong network like a mesh.
This network gives shape, support, and protection.
It resists stretching when water enters the cell.
Thus, the wall keeps the cell firm and prevents damage.
Q2. Explain how the cell wall helps plant cells in a hypotonic solution.
Answer:
A hypotonic solution has less solute than the cell sap.
Water enters the cell by osmosis through the plasma membrane.
The cell becomes turgid and swells.
The cell wall pushes back and creates turgor pressure.
This pressure stops the cell from bursting.
So, the wall helps maintain shape and integrity.
Q3. What is plasmolysis? Describe how you can observe it using a Rhoeo leaf.
Answer:
Plasmolysis is when the cell contents shrink away from the cell wall.
It happens when water is lost by osmosis in a hypertonic solution.
Take a peel of a Rhoeo leaf and mount it in water on a slide.
You will see chloroplasts spread in the cell.
Add a strong salt or sugar solution and wait.
The cell contents pull away from the wall. This shows plasmolysis.
Q4. Define osmosis and relate it to cell behavior in different solutions.
Answer:
Osmosis is the movement of water across a semipermeable membrane.
Water moves from a region of higher water concentration (lower solute) to lower water concentration (higher solute).
In a hypotonic solution, cells gain water and become turgid.
In a hypertonic solution, cells lose water and become plasmolysed.
In an isotonic solution, there is no net water movement.
This explains swelling, shrinking, and balance in plant cells.
Q5. Why do dead cells not show plasmolysis in the Rhoeo experiment?
Answer:
Living cells have an active plasma membrane.
This membrane is semipermeable and controls water movement.
When cells are boiled, they become dead.
The membrane loses its selective permeability.
Without this property, osmosis does not occur.
So, dead cells do not show plasmolysis.
High Complexity (Analysis & Scenario-Based)
Q6. A potted plant is watered with a strong salt solution by mistake. Predict what happens at the cellular level and to the plant’s appearance.
Answer:
The soil becomes hypertonic compared to the cell sap.
Water moves out of cells by osmosis.
Cell contents shrink from the cell wall (plasmolysis).
Turgor pressure falls, so cells lose firmness.
Leaves become flaccid and the plant wilts.
Prolonged exposure can cause permanent damage.
Q7. Compare a plant cell and an animal cell placed in a hypotonic solution. What role does the cell wall play?
Answer:
In a hypotonic solution, both cells gain water.
A plant cell’s cell wall resists expansion.
It builds turgor pressure and prevents bursting.
An animal cell has no cell wall.
It may swell too much and burst (lysis).
Thus, the cell wall ensures plant cell safety and shape.
Q8. During a lab, a student sees chloroplasts close to the cell wall in water but clustered near the center after adding salt solution. Explain these observations.
Answer:
In water, the cell is turgid due to inward water flow.
The cytoplasm pushes against the cell wall.
Chloroplasts appear spread near the wall.
After salt is added, the solution is hypertonic.
Water leaves the cell, and the protoplast shrinks.
Chloroplasts cluster inward, showing plasmolysis.
Q9. A classmate says, “Osmosis is water moving from low concentration to high concentration.” Correct this statement with an example.
Answer:
The correct idea is about water concentration, not solute alone.
Water moves from higher water concentration to lower water concentration.
Or from lower solute to higher solute across a semipermeable membrane.
Example: a cell in salt solution loses water to the outside.
The outside has higher solute and lower water.
This is why plasmolysis happens in strong salt or sugar solutions.
Q10. If the cell wall is weakened or partially removed, how will the cell behave in different solutions?
Answer:
With a weak or missing cell wall, the cell loses rigidity.
In a hypotonic solution, water enters by osmosis.
The cell may swell too much and can burst.
In a hypertonic solution, it shrinks quickly.
It cannot resist changes because turgor pressure is not balanced by a strong wall.
Thus, the cell wall is vital for shape, support, and safety.
