How are saturated fatty acids packed?

• A. tightly
• B. loosely
• C. randomly
• D. helically

Answer: (A)

Saturated fatty acids have straight hydrocarbon chains because their carbon–carbon bonds are all single bonds, so the tails can align closely with one another. This straight shape lets many molecules stack tightly, increasing van der Waals interactions and creating a dense, orderly packing. That tight arrangement is why fats rich in saturated fatty acids tend to be solid at room temperature and why their tails form a compact, rigid region in membranes. In contrast, double bonds in unsaturated fatty acids introduce kinks, preventing close packing and leading to looser, more fluid arrangements.