How many types of lipids are there?

Question

Yeah, and also, What are the functions and compositions of Lipids? And why are Lipids not soluble in water?

Answer 1

It depends on how you classify them, but to start there are triglycerides, phospholipids, sphingolipids, and steroids at least.

Lipids are the "everything else" category of macromolecules, so they sometimes don't have a lot in common.

But the major idea is that they are fat-soluble and not water-soluble (meaning that they are mostly hydrophobic). A common structure is that they have a "head" which is hydrophilic and is made of glycerol, plus 2 or more "tails" which are hydrophobic and made of fatty acids.

The reason that they aren't soluble in water is because of the fatty acid chains. They are long strings of carbon and so they are nonpolar, and repel water, really similar to oil.

Function: lipids have a variety of functions

Triglycerides are used for long-term energy storage and insulation (this is fat in the body)

Phospholipids make up the cell membrane in all living cells.

Sphingolipids and cholesterol are part of the cell membrane, they sort of hold it together.

Hormones and steroids are used in cell signalling (like testosterone and estrogen, among others).

Hope that helps!