Nucleus

a lake is surrounded by land on all sides!:)

Ok, I think you mean electons. The nucleus is made up of protons and neutrons, surrounded by electrons. An electron has a negative charge. It is so light, it has negligible mass. The atom Hydrogen has only one proton as its nucleus, surrounded by its one electron. Oxygen has, of the top of my head, 8? electrons. These electrons move in orbitals around the proton. Without going into complicated detail, that's all I can tell you I'm afraid.

If you are referring to 2 bodies of water, than your answer is: a penninsula.

The mitochondria and the chloroplast are organelles that have a double membrane.