Magnesium is an essential element present in the living organisms. For example, ATP which is the main source of energy is bound to a magnesium ion in its active form. Also, many enzymes requires magnesium ion for their function. Iron is another vital element of living organisms. It is part of various processes like oxygen transport, electron transport, DNA synthesis, etc. Sodium is the primary ion of the body fluid and helps in maintaining the blood pressure. It is also important in nerve action. Silicon is not found in the living organisms.