What lipids are hydrophilic?

• A. Phospholipids, acid lycolipids, neutral glycolipids
• B. Cholesterol esters
• C. Mono/diglycerides
• D. Waxes

Answer: (A)

Lipids differ in how they interact with water because of their polar groups. Hydrophilicity comes from polar, water-attracting heads. Phospholipids have a phosphate-containing head that is highly polar and often charged, so that part loves water while the fatty acid tails are nonpolar. Glycolipids also have sugar-containing heads, which are hydrophilic and draw water to the surface. When a lipid has these polar heads, it behaves as an amphipathic molecule, with the head engaging the aqueous environment. That’s why phospholipids and glycolipids are hydrophilic overall.

In contrast, cholesterol esters, mono- and diglycerides, and waxes are largely nonpolar and lack polar head groups, so they are hydrophobic and do not mix well with water.