alleryStart learning →Which part of a phospholipid interacts with water?
AThe fatty acid tails, which are hydrophilic
BThe phosphate containing head, which is hydrophilic
CBoth the tails and the head, which are hydrophilic
DNeither part, as the whole molecule is hydrophobic
Answer & Solution
Correct answer: B. The phosphate containing head, which is hydrophilic
1. A phospholipid is amphipathic, meaning it has a hydrophobic part and a hydrophilic part.
2. The fatty acid chains are hydrophobic and cannot interact with water, and they form the tail.
3. The phosphate containing group is hydrophilic and does interact with water, and it forms the head.
4. In a membrane bilayer the tails face inward, away from water, while the phosphate heads face the aqueous side.
5. Calling the whole molecule hydrophobic would leave no reason for a bilayer to form at all.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 3 "Biological Macromolecules", section 3.3 Lipids_
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