Why is the selective permeability of the plasma membrane essential for normal cell function?

• A. It prevents any substances from entering or leaving the cell, maintaining complete isolation.
• B. It allows the cell to randomly exchange substances with the environment, ensuring diversity.
• C. It enables the cell to absorb all substances from the external environment without restriction.
• D. It allows the cell to maintain a stable internal environment by regulating the entry and exit of substances.

Answer: (D)

Verified step by step guidance

1. Understand the concept of selective permeability: Selective permeability refers to the ability of the plasma membrane to regulate the passage of substances in and out of the cell. This is crucial for maintaining homeostasis within the cell.
2. Recognize the role of the plasma membrane: The plasma membrane is composed of a phospholipid bilayer with embedded proteins. These proteins act as channels and carriers that facilitate the selective transport of molecules.
3. Identify the importance of regulation: By controlling what enters and exits the cell, the plasma membrane ensures that essential nutrients are absorbed, waste products are expelled, and harmful substances are kept out, thus maintaining a stable internal environment.
4. Consider the consequences of non-selective permeability: If the plasma membrane allowed all substances to pass freely, the cell would be unable to maintain its internal conditions, leading to potential damage or dysfunction.
5. Relate selective permeability to cell function: The ability to regulate substance exchange is vital for processes such as nutrient uptake, ion balance, and communication with other cells, all of which are essential for normal cell function.