What type of molecule is described as having both a hydrophilic region and a hydrophobic region?

• A. Lipid
• B. Amphipathic
• C. Protein
• D. Nucleotide

Answer: (B)

Molecules that possess both a hydrophilic region and a hydrophobic region are classified as amphipathic. This term specifically describes the dual nature of these molecules, where one part can interact with water (hydrophilic) while another part is repelled by water (hydrophobic). This property is crucial in biological systems, particularly in the formation of cell membranes, where amphipathic molecules like phospholipids arrange themselves in a bilayer to create a barrier that separates the internal environment of the cell from the external environment.

In contrast, lipids typically include a broader category of molecules that may not necessarily have both regions; while phospholipids (a type of lipid) are amphipathic, other lipids like triglycerides are completely hydrophobic. Proteins and nucleotides can also have varying structures and properties, but they do not specifically define the characteristic of having both hydrophilic and hydrophobic regions as a primary feature. Hence, amphipathic accurately describes molecules that display this unique dual behavior.