Why must all living cells carefully regulate the fluidity of their membranes?

• A. To ensure proper function of membrane proteins and maintain selective permeability.
• B. To increase the rate of DNA replication within the nucleus.
• C. To prevent the cell from using energy during passive transport.
• D. To allow the membrane to become completely rigid for structural support.

Answer: (A)

Verified step by step guidance

1. Understand the role of the cell membrane: The cell membrane is a phospholipid bilayer that serves as a barrier and regulates the movement of substances in and out of the cell. It also houses membrane proteins that are essential for various cellular functions.
2. Recognize the importance of fluidity: Membrane fluidity is crucial for the proper functioning of membrane proteins, such as transport proteins, receptors, and enzymes. These proteins require a certain level of flexibility in the membrane to change shape and perform their functions effectively.
3. Consider selective permeability: The cell membrane must maintain selective permeability, allowing specific molecules to pass through while blocking others. Fluidity ensures that the membrane can adapt to changes in the environment and maintain this selective permeability.
4. Eliminate incorrect options: Increasing the rate of DNA replication within the nucleus is unrelated to membrane fluidity. Preventing energy use during passive transport is not a direct function of fluidity, as passive transport occurs naturally without energy. Making the membrane completely rigid would hinder its ability to function properly.
5. Conclude the correct answer: The regulation of membrane fluidity is essential to ensure proper function of membrane proteins and maintain selective permeability, which are critical for the survival and function of living cells.