Sorry! I got lost in a P91 fog.
3-hydroxy-13-methyl-12,14,15,16-tetrahydro-11H-cyclopenta[a]phenanthren-17*-one* - Equilin - is pictured below on the left. As you can see, there is a hydoxyl group attached on the left. This position is carbon 3.
It also has a a double bonded O at carbon 17, so it is a ketone (-one).
3-hydroxy-13-methyl-6,7,8,9,11,12,13,14,15,16- decahydrocyclopenta[a]phenanthren-17- one - Estrone - is pictured below on the right. It also has a hydroxyl group at position 3, and a double bonded O at position 17, and is also a ketone.
The difference between the two is the extra double bond C=C in the second ring of equilin and the position in space of the hydrogens. A double bond changes the shape of the molecule, as well as its functionality with regards to its free energy of activation. The free energy of activation determines how reactive a chemical compound is.
So, even though the two sound somewhat similar, are both contain a hydroxyl and a ketone groups at the same positions, and look very similar on paper, they are completely different.
Diane
Edit: Sorry, I need these pictures for another thread: Can someone identify this molecule: is it Meo-Est?