Water diffusion is called osmosis. Oxygen is a small molecule and it's nonpolar, so it easily passes through a cell membrane. Carbon dioxide, the byproduct of cell respiration, is small enough to readily diffuse out of a cell. Small uncharged lipid molecules can pass through the lipid innards of the membrane.
The sequence of Nucleotides in a DNA molecule determine the protein that will be produced. Nucleotides are the basic structural unit of DNA.
