Problem 66 - Objective Biology for NEET

Question

What happens when plant cell is put in hypotonic solution? (a) Cell swells up (b) Cell undergoes plasmolysis (c) Cell wall shrinks (d) Cell will burst

Step-by-Step Solution

Answer

(a) Cell swells up

Step 1: Understand Osmosis

Osmosis is a process where a solvent moves from an area of low solute concentration to an area of high solute concentration. In the context of cells, the solvent is water and solutes are elements like salts, sugars, and proteins inside the cells.

Step 2: Understand Hypotonic Solution

A hypotonic solution is a solution that has less solute concentration than the cytoplasm of a cell. Thus there's more water outside the cell, and water will move from outside to inside the cell due to difference in solute concentrations.

Step 3: Analyze the effect on a plant cell in a Hypotonic Solution

When a plant cell is put in a hypotonic solution, water enters the cell due to osmosis. The additional water fills the central vacuole and exerts a pressure against the cell wall, causing the cell to swell. However, plants have a rigid cell wall that can withstand this pressure and prevent the cell from bursting. Thus, even though the cell swells, it will not burst. This process is known as turgid.

Key Concepts

Hypotonic Solution

In the world of biology, solutions play a key role in cellular function. A **hypotonic solution** has a lower concentration of solutes compared to the cytoplasm inside a plant cell. This means it has more water outside. Consequently, water will naturally move into the cell by osmosis. This movement from an area where water is more abundant to an area where it is less abundant is essential. It allows cells to absorb water and nutrients efficiently.

• In a hypotonic solution, a plant cell absorbs water.
• The difference in solute concentration drives the water movement.
• Osmosis is crucial for maintaining cellular functions and overall plant health.

Turgor Pressure

As water flows into a plant cell in a hypotonic solution, it collects in the central vacuole. This accumulation creates **turgor pressure**, the pressure of the cell contents against the cell wall. It is crucial in maintaining the structural integrity of the plant.
Turgor pressure helps:

• Support plant tissues, aiding them to stay upright.
• Regulate the opening and closing of stomata, which are tiny openings on leaves.
• Facilitate growth by promoting cell expansion.

Without adequate turgor pressure, plants might wilt, indicating water deficiency.

Cell Wall Function

The **cell wall** is like a sturdy framework for plant cells. It offers protection and structure, particularly important when the cell is in a hypotonic solution. As water enters, the cell inflates, but the cell wall prevents it from bursting by providing resistance.
The cell wall also:

• Supports large vacuoles by balancing internal pressure.
• Helps in maintaining the specific shape of the plant cell.
• Permits a degree of flexibility, allowing cells to grow.

This structural feature is unique to plant cells and some algae, giving them rigidity and protection.

Plasmolysis Prevention

**Plasmolysis** occurs when the plant cell loses water, typically in a hypertonic environment, causing the cell membrane to pull away from the cell wall. In a hypotonic solution, the risk of plasmolysis is extremely low, as the cell tends to absorb water instead. Preventing plasmolysis is essential for plant cell survival.
Steps that reduce plasmolysis risk include:

• Maintaining a suitable environment with adequate water levels.
• Ensuring that plant cells remain in hypotonic or isotonic solutions.
• Replenishing water levels to encourage healthy turgor pressure.

By doing so, plants can sustain their turgor pressure and overall metabolism, promoting healthy plant life.