How do phospholipid molecules contribute to the compartmentalization of a cell?

• A. They actively transport ions across the membrane to create compartments.
• B. They form a bilayer with hydrophobic tails facing inward and hydrophilic heads facing outward, creating selective barriers between cellular compartments.
• C. They bind directly to DNA to separate genetic material from the cytoplasm.
• D. They polymerize into rigid structures that provide mechanical support to the cell.

Answer: (B)

Verified step by step guidance

1. Understand the structure of a phospholipid molecule: A phospholipid consists of a hydrophilic (water-attracting) head and two hydrophobic (water-repelling) tails. This amphipathic nature is key to their role in cell compartmentalization.
2. Recognize how phospholipids arrange themselves in an aqueous environment: Due to their amphipathic nature, phospholipids spontaneously form a bilayer. The hydrophilic heads face outward toward the water, while the hydrophobic tails face inward, away from the water.
3. Explain how the bilayer creates compartments: The phospholipid bilayer acts as a selective barrier, separating the internal environment of the cell from the external environment. It also forms internal compartments, such as organelles, by enclosing specific regions within the cell.
4. Clarify the selective permeability of the bilayer: The bilayer allows certain molecules (e.g., small nonpolar molecules) to pass through while restricting others (e.g., large polar molecules or ions). This selective permeability is crucial for maintaining distinct cellular environments.
5. Summarize the role of phospholipids in compartmentalization: By forming a bilayer with hydrophobic and hydrophilic regions, phospholipids create physical and functional boundaries that enable the cell to maintain homeostasis and carry out specialized functions in different compartments.