Key structural differences in lipids Steps:

• Recall phospholipid structure: one glycerol with two fatty acids and one phosphate group attached via ester and phosphoester bonds.
• Recall triglyceride structure: one glycerol with three fatty acids attached via ester bonds.
• Compare components: phospholipids have two fatty acids for amphipathic properties; triglycerides have three for hydrophobicity and energy storage.
• Match to choice stating fewer fatty acids in phospholipids versus more in triglycerides.

Why D is correct:

• Phospholipids incorporate two fatty acid chains into a diacylglycerol-phosphate, while triglycerides form from triacylglycerol with three chains, per standard biochemical formulas.

Why the others are wrong:

• A: Phospholipids are amphipathic overall, not defined solely by a hydrophilic phosphate; ignores shared hydrophobic tails.
• B: Ester bond count mirrors fatty acid number (two vs. three), making this redundant and less direct than fatty acid comparison.
• C: Both contain one glycerol molecule; triglycerides use a single glycerol, not three.

Final answer: D