What purpose do transmembrane proteins serve in the cell membrane?

• A. They provide structural support to the cell membrane.
• B. They are involved in the synthesis of lipids.
• C. They act as channels or transporters for molecules across the membrane.
• D. They function as enzymes for intracellular reactions.

Answer: (C)

Verified step by step guidance

1. Understand the structure of the cell membrane: The cell membrane is composed of a phospholipid bilayer with embedded proteins, including transmembrane proteins.
2. Identify the role of transmembrane proteins: These proteins span the entire membrane and are crucial for transporting molecules across the membrane.
3. Differentiate between types of transmembrane proteins: Some act as channels, allowing specific molecules or ions to pass through, while others function as transporters, actively moving substances across the membrane.
4. Consider the importance of selective permeability: Transmembrane proteins contribute to the cell membrane's selective permeability, which is essential for maintaining homeostasis by regulating the internal environment of the cell.
5. Recognize other functions of transmembrane proteins: Besides transport, they can also serve as receptors for signal transduction, linking the external environment to the cell's internal processes.