Why do cells have a plasma membrane? 1.to distinguish plants from animals
2.to define the size of the cell
3.to separate the inside of the cell from its environment
4.to separate proteins from the nucleus
also here is a anime pic to make the day even better

"hydrogen bonding is the attraction of h atoms in the water molecule (slight + charge) to o atoms in a neighboring water molecule (slight - charge); it is a weak interatomic force. but it is still strong enough to the water molecules "stick" together."

answer: they produce more slow than unicellular organisms.