Describe how the common cell is the root of multicellular organism diversity.

Cells are primarily made up of four elements: carbon, oxygen, hydrogen, and nitrogen in addition to smaller amounts of other elements. The major building material of the cell is protein. Cells are all different in size and shape. The shape reflects function. All cells exhibit irritability, digest foods, excrete wastes, and are able to reproduce, grow, move, and metabolize. Cells transport substances through the cell membrane either by passive transport or active transport. Osmotic pressure determines if cells gain or lose water. Cell division has two phases, mitosis and cytokinesis. Protein synthesis involves DNA and RNA.