Most of the skin cells on the very outside of your skin are actually dead, so the most important thing that these molecules do is to hold them together. The next type of molecule is proteins. Proteins contain Hydrogen, Carbon, Oxygen, Nitrogen, and usually Sulfur atoms. These are things like hormones and enzymes and all sorts of other things. One common protein in skin cells is called keratin.
Keratin is a large, complicated molecule that makes cells stronger.
This is important for skin cells, because they rub up against things a lot. The last major type of organic molecule is nucleic acids. These contain Hydrogen, Carbon, Oxygen, Nitrogen, and Phosphorus atoms. DNA is the most important part of any cell, because it contains the information that determines what your body is. For example, your DNA determines whether you'll have blue eyes or brown eyes and whether you'll be tall or short.