What defines an amphipathic molecule?

• A. It is completely hydrophilic
• B. It has only hydrophobic parts
• C. It has both hydrophilic and hydrophobic parts
• D. It is always a larger molecule

Answer: (C)

An amphipathic molecule is uniquely characterized by having both hydrophilic (water-attracting) and hydrophobic (water-repelling) regions within its structure. This duality allows amphipathic molecules to interact with both polar and non-polar substances, which is particularly important in biological systems. For instance, phospholipids, a class of amphipathic molecules, have hydrophilic heads that interact with water and hydrophobic tails that avoid water, enabling them to form cell membranes.

This property is paramount in creating structures such as lipid bilayers, which serve as barriers and compartments in biological cells. The presence of both types of regions in an amphipathic molecule is fundamental to its ability to participate in various chemical interactions and biological processes, such as membrane formation and the solubilization of different substances in mixed environments.