Minerals make up about 4% of total body weight. They are primarily found in bones and teeth. Cells use minerals to make enzymes, cell membranes, and various proteins such as hemoglobin. The most important miner als to the human body are calcium, phosphorus, sulfur sodium, chlorine, and magnesium. Trace elements are ele- ments needed in very small amounts by the body. They include iron, manganese, copper, iodine, and zinc.