NCERT Class 9 Science — Chapter 1: The fundamental unit of life

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A plant cell is placed in a hypertonic solution. Which of the following phenomena is most likely to occur?

Official previous-year question

Verified 1 Aug 2026.

Options

AThe cell will swell and eventually burst.
BThe cell will maintain its shape with no net movement of water.
CThe cell wall will dissolve into the solution.
DThe cell contents will shrink away from the cell wall.

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Solution

The correct option is

The cell contents will shrink away from the cell wall.

Explanation

The movement of water across a semi-permeable membrane is governed by osmosis. The direction of water flow depends on the tonicity of the external solution relative to the cell sap:

Hypertonic Solution: Higher solute concentration (lower water potential) outside the cell.
Hypotonic Solution: Lower solute concentration (higher water potential) outside the cell.
Isotonic Solution: Equal solute concentration on both sides.

Option Analysis

The cell will swell and eventually burst. is Incorrect: A cell swells when placed in a hypotonic solution because water enters the cell (endosmosis). In plant cells, the rigid cell wall prevents bursting, leading to turgidity.
The cell will maintain its shape with no net movement of water. is Incorrect: A cell maintains its shape with no net movement of water only when placed in an isotonic solution, where the osmotic pressure inside and outside the cell is in equilibrium.
The cell contents will shrink away from the cell wall. is Correct: When a plant cell is placed in a hypertonic solution, water moves out of the cell into the external solution (exosmosis). As the central vacuole loses water, the protoplast (cell membrane and internal contents) shrinks and pulls away from the rigid cell wall. This phenomenon is known as plasmolysis.
The cell wall will dissolve into the solution. is Incorrect: The cell wall is composed of cellulose, a structural polysaccharide that provides rigidity. It does not dissolve merely due to changes in the osmotic concentration of the surrounding solution.

Key Takeaway

Plasmolysis occurs when a plant cell is placed in a hypertonic solution, causing water to leave the cell via exosmosis, resulting in the shrinkage of the protoplast away from the cell wall.

Your note

More from Chapter 1: The fundamental unit of life

With reference to Plastids, consider the following statements: 1. They are present only in plant cells. 2. Chromoplasts are colourless plastids, while leucoplasts contain chlorophyll. 3. Unlike mitochondria, plastids lack their own DNA and ribosomes. Which of the statements given above is/are correct?

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Which of the following pairs is correctly matched?

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Consider the following statements about Vacuoles: 1. They are small-sized in animal cells while plant cells have very large vacuoles. 2. In Amoeba, the food vacuole is absent. 3. They can play a role in expelling excess water from the cell. Which of the statements given above is/are correct?

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With reference to osmosis, consider the following statements: 1. Osmosis is the net diffusion of water across a selectively permeable membrane. 2. If a cell is placed in a hypotonic solution, it is likely to shrink. 3. Water molecules pass across the membrane in only one direction during osmosis. Which of the statements given above is/are correct?

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Consider the following statements regarding the cell wall: 1. It is present in plants, fungi, and bacteria. 2. It is mainly composed of lipids which provide structural strength. 3. It enables cells to withstand very dilute external media without bursting. Which of the statements given above is/are correct?

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The correct option is

The cell contents will shrink away from the cell wall.

Explanation

The movement of water across a semi-permeable membrane is governed by osmosis. The direction of water flow depends on the tonicity of the external solution relative to the cell sap:

Hypertonic Solution: Higher solute concentration (lower water potential) outside the cell.
Hypotonic Solution: Lower solute concentration (higher water potential) outside the cell.
Isotonic Solution: Equal solute concentration on both sides.

Option Analysis

The cell will swell and eventually burst. is Incorrect: A cell swells when placed in a hypotonic solution because water enters the cell (endosmosis). In plant cells, the rigid cell wall prevents bursting, leading to turgidity.
The cell will maintain its shape with no net movement of water. is Incorrect: A cell maintains its shape with no net movement of water only when placed in an isotonic solution, where the osmotic pressure inside and outside the cell is in equilibrium.
The cell contents will shrink away from the cell wall. is Correct: When a plant cell is placed in a hypertonic solution, water moves out of the cell into the external solution (exosmosis). As the central vacuole loses water, the protoplast (cell membrane and internal contents) shrinks and pulls away from the rigid cell wall. This phenomenon is known as plasmolysis.
The cell wall will dissolve into the solution. is Incorrect: The cell wall is composed of cellulose, a structural polysaccharide that provides rigidity. It does not dissolve merely due to changes in the osmotic concentration of the surrounding solution.

Key Takeaway

Plasmolysis occurs when a plant cell is placed in a hypertonic solution, causing water to leave the cell via exosmosis, resulting in the shrinkage of the protoplast away from the cell wall.