Problem 51 - Objective Biology for NEET

Question

A cell placed in strong solution will shrink because (a) Cytoplasm will decompose (b) Mineral salt will break the cell wall (c) Salt water enter the cell (d) Water comes out by exosmosis

Step-by-Step Solution

Answer

(d) Water comes out by exosmosis

Step 1: Understand the Concept of Osmosis

Osmosis is a process in which molecules of a solvent (usually water) pass through a semipermeable membrane from a less concentrated solution into a more concentrated one, equalizing the concentrations on each side of the membrane.

Step 2: Relate the Concept to a Cell in a Solution

A cell is a semipermeable entity. When we place it in a strong solution (a hypertonic solution, which is more concentrated than the cell's internal environment), water will move from the less concentrated area (inside the cell) to the more concentrated one (the surrounding solution). This leads to a decrease in the cell's volume or shrinkage.

Step 3: Match the Explanation to the Correct Option

Looking at the provided options, (a) and (b) do not describe this process. (c) is also incorrect as it describes an opposite process. Option (d) Water comes out by exosmosis is the accurate description of the water movement due to the osmotic pressure. Exosmosis is the movement of water molecules from the cell to the outside through the cell membrane.

Key Concepts

Exosmosis

Exosmosis is a specific type of osmosis that occurs when water molecules move out of the cell. Imagine you have a cell sitting in a more concentrated surrounding, meaning the outside solution has a higher concentration of solutes compared to inside the cell. In such cases, water will naturally flow out of the cell, aiming to balance the concentrations.
This is called exosmosis. As water leaves, the cell tends to shrink. This process is crucial for maintaining cellular balance and understanding how cells interact with their environments.

• Exosmosis occurs when a cell is placed in a hypertonic solution.
• It leads to the shrinkage of the cell as water exits.
• This movement is driven by the aim to balance solute concentrations between the cell and its environment.

Understanding exosmosis helps explain why certain cells shrivel when exposed to environments where the concentration outside the cell is greater than within its boundaries.

Semipermeable Membrane

A semipermeable membrane is a vital component in many biological processes. It is a type of barrier that allows some particles to pass while blocking others. This selective permeability is essential for processes like osmosis. Within biological systems, cell membranes function as semipermeable membranes.
They let water molecules pass while keeping many solutes from doing the same, controlling the movement of substances in and out of cells.

• Semipermeable membranes allow water to move freely but restrict many solutes.
• They are crucial for maintaining the cell's internal environment and enabling processes like osmosis.
• This membrane's selective nature ensures that cells can regulate their internal conditions efficiently.

Understanding semipermeable membranes helps underscore their role in maintaining cellular health and function.

Hypertonic Solution

A hypertonic solution is one with a higher concentration of solutes than the cell's internal fluid. When a cell is placed in this type of solution, it experiences water loss. The water inside the cell moves out through the semipermeable membrane to try to equalize solute concentrations.
This movement concerns osmosis and leads to cell shrinkage, a process often observed in plant cells exposed to saline environments.

• Hypertonic solutions have more solutes outside the cell than inside.
• Cells in hypertonic environments lose water and become smaller.
• Understanding hypertonicity is important for appreciating how cells manage osmotic pressure and balance.

Grasping the concept of hypertonic solutions helps one understand the conditions leading to exosmosis and the role of semipermeable membranes in cellular protection.