Question

Describe two ways that steroids differ from fats.

Answer 1

I already have one - need another: structurally, fats have glycerol backbone and three fatty acid chains, while steroids have four fused rings. any others?

Answer 2

Biochemically, steroids play a very different role. Steroids are biochemically more active than fats. Some of the most potent molecules are steroids - testosterone, corticosteroids etc.
Structurally steroids provide rigidity to the membranes while fatty acids provide liquidity or flexibility.

Answer 3

I started to write that, but then figured out that the question is about actual physical properties of sterols instead of their role in biomembranes, signalling, etc.

Answer 4

if you talk structural, then I can say something as well.

if you put a steroid into a membran, that membrane will behave differently from a membrane made of phospholipids. steroids are sterically more demanding and not as flexible, so your membrane will be more rigid and will endure higher temperatures.

also, since fatty acids are easily degraded by phospholipases and steroids take more difficult mechanisms to digest, they are more attuned to their task as long-lasting hormones like testosterone.