* oxygen (O), 65% body weight, found in water
* carbon (C) 18% body weight, found in organic molecules
* hydrogen (H), 10% body weight, found in most molecules, including water
* nitrogen (N), 3% body weight, component of proteins
* calcium (Ca), 2% body weight, component of bones, teeth, and body fluids
* phosphorus (P), 1% body weight, found in cell membranes and bone matrix