Problem 61 - Objective Biology for NEET

Question

Which of the following is not the function of cell wall? (a) Interaction with outside world (b) Provide structural support and shape (c) Prevent from bursting and collapsing (d) Exchange of nutrition takes place through it

Step-by-Step Solution

Answer

The function that is not of a cell wall is (d) Exchange of nutrition takes place through it.

Step 1: Understand the Cell Wall Functions

The cell wall in an organism is primarily responsible for providing structural support, preventing the cell from bursting or collapsing, and interfacing with the surrounding environment.

Step 2: Identify the Not Function

Now, match these functions with the options given in the exercise. Options (a), (b), and (c) are all general functions of the cell wall. However, option (d) - exchange of nutrition takes place through it, is not a primary function of the cell wall. The exchange of materials in and out of the cell mainly happens through different cellular structures, like the cell membrane or the cytoplasm.

Key Concepts

Structural Support

The primary function of the cell wall is to provide structural support to the cell. The cell wall is a rigid layer that surrounds the cell, giving it strength and stability. This structure is especially important in plant cells, fungi, and certain bacteria. It helps maintain the shape of the cell despite the external pressures that may be applied.

The cell wall is composed of various materials like cellulose in plants, chitin in fungi, and peptidoglycan in bacteria. These materials form a tough and protective layer that keeps the shape consistent. Without the support of the cell wall, the cell would be soft and unable to retain its structure.

• Maintains the cell's shape.
• Provides rigidity against external forces.
• Supports the structured growth of tissues and organs.

Overall, the cell wall's role in providing structural support ensures that cells can withstand environmental stresses without losing their form.

Cell Bursting Prevention

Another vital function of the cell wall is to prevent cell bursting, a process formally known as lysis. The cell wall acts as a pressure vessel that allows cells to hold significant osmotic pressure without bursting. When water enters the cell, it creates pressure against the cell wall. The wall's integrity prevents the cell from exploding even when inner pressures are high.

This capability is crucial in aquatic environments or during abnormal hydration conditions where an influx of water might occur. Without this protection, cells cannot maintain their integrity under pressure, leading to cell damage or death.

• Acts as a barrier against excessive water intake.
• Prevents cell lysis under osmotic pressures.
• Helps in maintaining homeostasis under varying external conditions.

Thus, the cell wall's function in preventing bursting is essential for cell survival in different environments.

Material Exchange

While the cell wall is incredibly functional, it is not primarily responsible for the exchange of materials. That task mainly belongs to the cell membrane, which is more flexible and semi-permeable. The cell wall does, however, play a passive role in this process by providing a structure for biochemical exchanges.

The cell membrane manages the controlled entry and exit of nutrients, gases, and wastes. It acts as a selective barrier, allowing some substances to pass while blocking others. On the other hand, structures like plasmodesmata, which are channels through the cell wall, facilitate limited exchange.

• Cell membrane plays the central role in material exchange.
• The cell wall aids through structural integrity, not direct exchange.
• Plasmodesmata provide passageways in plant cells.

Therefore, material exchange is managed by other cellular structures, even as the cell wall provides the framework supporting the overall cellular function.