The fat-soluble vitamins are Vitamins A, D, E, and K.
Here are their structures.
Vitamin A
Vitamin D
Vitamin E
Vitamin K
Why are they fat-soluble?
Here is the structure of a typical fat.
The molecule is almost completely a nonpolar hydrocarbon.
Its intermolecular forces are mostly London dispersion forces.
Now, look at the structures of the fat-soluble vitamins.
They, too, are almost completely nonpolar hydrocarbon molecules.
Their intermolecular forces are mostly London dispersion forces, so each can mingle freely with the molecules of the fats in our bodies.
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