it separates the inside of the cell from the environment outside and it controls substances moving in and out of the cell (selectively permeable)
In water molecule the electrons between the oxygen and the hydrogen are shared, but the sharing is not equal. Oxygen pulls electrons slightly towards itself. Therefore, the electrons are more near the oxygen, making that part of molecule(oxygen part) slightly negative. Since the electrons are not near the hydrogen so, that part of the molecule is slightly positive.
The limbic system is mostly related to emotional behaviours
The answer is nucleotides