: Carbon, oxygen, hydrogen and nitrogen are the major constituents of most biomolecules. Protoplasm is made up mainly of C,H,O, and N, which make up 95% by weight of the body. The proportions of various elements in protoplasm is - oxygen (65%), carbon (8%), hydrogen (10%), nitrogen (3%), calcium (2.5%), phosphorus (1.14%), chlorine (0.15%), sulphur (0.16%) and potassium, sodium, magnesium, iodine, iron etc. are in traces.