Why do lipids not mix with water? A) They are highly soluble in water B) They are hydrophobic, meaning they repel water C) They are acidic and dissolve in water D) They form hydrogen bonds with water

The correct answer is: **B) They are hydrophobic, meaning they repel water** **Explanation:** Lipids are **hydrophobic** molecules, which means they do not interact well with water. This is primarily due to their long hydrocarbon chains, which are nonpolar and do not form favorable interactions with water molecules, which are polar. Instead of mixing with water, lipids tend to aggregate together, minimizing their exposure to the aqueous environment. This property is essential for the formation of biological membranes, where lipids arrange themselves into bilayers, creating a barrier that separates the inside of cells from their external environment. Here's a brief overview of why the other options are incorrect: - **A) They are highly soluble in water:** This is incorrect. Lipids are not soluble in water; they are insoluble due to their hydrophobic nature. - **C) They are acidic and dissolve in water:** While some lipids can be acidic (like fatty acids), this does not make them dissolve in water. Their overall hydrophobic characteristics prevent them from dissolving. - **D) They form hydrogen bonds with water:** Lipids generally do not form hydrogen bonds with water. Instead, they avoid interacting with water molecules, leading to their hydrophobic behavior. **Key Takeaway:** The hydrophobic nature of lipids prevents them from mixing with water, leading to their characteristic behavior in biological systems.