Which part of a phospholipid is polar (hydrophilic)?

Which part of a phospholipid is polar (hydrophilic)?

• A. Phosphate Head (Polar)
• B. Fatty Acid Tails (Non-Polar)
• C. Both Head and Tails Polar and Non-Polar
• D. The Glycerol Backbone Only

Answer: (A)

This question tests polarity in a phospholipid. The polar, hydrophilic part is the phosphate-containing head. That head carries charge and can form hydrogen bonds with water, so it readily interacts with the aqueous environment. The fatty acid tails are long hydrocarbon chains that are non-polar and water-fearing, which is why they form the non-polar interior of lipid bilayers. The glycerol backbone links these regions but isn’t the polar, water-attracting part—the phosphate head is what drives the molecule’s interaction with water. This amphipathic arrangement underlies how phospholipids form cellular membranes, with heads facing the watery surroundings and tails tucked away from water.

This question tests polarity in a phospholipid. The polar, hydrophilic part is the phosphate-containing head. That head carries charge and can form hydrogen bonds with water, so it readily interacts with the aqueous environment. The fatty acid tails are long hydrocarbon chains that are non-polar and water-fearing, which is why they form the non-polar interior of lipid bilayers. The glycerol backbone links these regions but isn’t the polar, water-attracting part—the phosphate head is what drives the molecule’s interaction with water. This amphipathic arrangement underlies how phospholipids form cellular membranes, with heads facing the watery surroundings and tails tucked away from water.