Which component is not part of a phospholipid?

Which component is not part of a phospholipid?

• A. Glycerol backbone
• B. Phosphate group
• C. Two fatty acid tails
• D. Three fatty acid tails

Answer: (D)

Phospholipids are built around a glycerol backbone with a hydrophobic interior formed by two fatty acid tails and a hydrophilic head formed by a phosphate group (often with another small molecule attached). This arrangement gives the molecule its amphipathic character, which drives membrane formation. If three fatty acid tails were present, there would be no phosphate-containing head to provide a polar region; such a molecule would be a triglyceride, not a phospholipid. So the component that is not part of a phospholipid is having three fatty acid tails.

Phospholipids are built around a glycerol backbone with a hydrophobic interior formed by two fatty acid tails and a hydrophilic head formed by a phosphate group (often with another small molecule attached). This arrangement gives the molecule its amphipathic character, which drives membrane formation. If three fatty acid tails were present, there would be no phosphate-containing head to provide a polar region; such a molecule would be a triglyceride, not a phospholipid. So the component that is not part of a phospholipid is having three fatty acid tails.