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?

The correct option is (a). Explanation Osmosis is a specific type of passive transport involving the movement of solvent molecules (typically water) across a semi-permeable membrane to equalize solute concentrations on either side. Statement-wise Analysis: - Statement 1 is Correct: Osmosis is defined as the net diffusion of water across a selectively permeable membrane from a region of higher water potential (lower solute concentration) to a region of lower water potential (higher solute concentration). - Statement 2 is Incorrect: A hypotonic solution has a lower solute concentration than the cell's cytoplasm. When a cell is placed in a hypotonic solution, water enters the cell via osmosis, causing it to swell or become turgid. Cells shrink (plasmolysis) only when placed in a hypertonic solution. - Statement 3 is Incorrect: Molecular movement is random and continuous. Water molecules cross the membrane in both directions simultaneously. Osmosis refers to the net movement of water, which occurs directionally towards the region of higher solute concentration, but individual molecular movement is not unidirectional. Key Takeaway: Osmosis describes the net flow of water down its concentration gradient; however, the movement of individual water molecules across the membrane remains bidirectional due to kinetic energy.

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

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With reference to osmosis, consider the following statements:

Osmosis is the net diffusion of water across a selectively permeable membrane.
If a cell is placed in a hypotonic solution, it is likely to shrink.
Water molecules pass across the membrane in only one direction during osmosis.

Which of the statements given above is/are correct?

Official previous-year question

Verified 1 Aug 2026.

Options

A1 only
B2 only
C1 and 3 only
D1, 2 and 3

Did you get this right?

Solution

The correct option is (a).

Explanation

Osmosis is a specific type of passive transport involving the movement of solvent molecules (typically water) across a semi-permeable membrane to equalize solute concentrations on either side.

Statement-wise Analysis:

Statement 1 is Correct: Osmosis is defined as the net diffusion of water across a selectively permeable membrane from a region of higher water potential (lower solute concentration) to a region of lower water potential (higher solute concentration).
Statement 2 is Incorrect: A hypotonic solution has a lower solute concentration than the cell's cytoplasm. When a cell is placed in a hypotonic solution, water enters the cell via osmosis, causing it to swell or become turgid. Cells shrink (plasmolysis) only when placed in a hypertonic solution.
Statement 3 is Incorrect: Molecular movement is random and continuous. Water molecules cross the membrane in both directions simultaneously. Osmosis refers to the net movement of water, which occurs directionally towards the region of higher solute concentration, but individual molecular movement is not unidirectional.

Key Takeaway: Osmosis describes the net flow of water down its concentration gradient; however, the movement of individual water molecules across the membrane remains bidirectional due to kinetic energy.

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The correct option is (a).

Explanation

Osmosis is a specific type of passive transport involving the movement of solvent molecules (typically water) across a semi-permeable membrane to equalize solute concentrations on either side.

Statement-wise Analysis:

Statement 1 is Correct: Osmosis is defined as the net diffusion of water across a selectively permeable membrane from a region of higher water potential (lower solute concentration) to a region of lower water potential (higher solute concentration).
Statement 2 is Incorrect: A hypotonic solution has a lower solute concentration than the cell's cytoplasm. When a cell is placed in a hypotonic solution, water enters the cell via osmosis, causing it to swell or become turgid. Cells shrink (plasmolysis) only when placed in a hypertonic solution.
Statement 3 is Incorrect: Molecular movement is random and continuous. Water molecules cross the membrane in both directions simultaneously. Osmosis refers to the net movement of water, which occurs directionally towards the region of higher solute concentration, but individual molecular movement is not unidirectional.