Eek!! I see lots of trans-fats in the above example
The low-down.
If all the "fat tails" are straight, they can pack in tightly as the fat cools ... allowing the formation of a solid.
If most "fat tails" are bent, the fat can not pack in tightly, maintaining fluidity.
Your cell's plasma membrane uses cholesterol to regulate membrane fluidity (prevents tails from packing in tightly at low temperatures).