General Chemistry

Introduction: Iron in the Body

The Body as a Chemical System: Chemical Elements that Make Up the Body

What are our bodies made of, and how do they work? These questions are fundamental to the study of medicine and to many chemists, biologists, and engineers. We know that our bodies are matter, and thus must be composed of atoms that have been specially arranged to produce the molecules and larger structures that sustain our lives. We know that the properties of an atom (e.g., size, electronegativity, number of valence electrons) determine how that atom will interact with other atoms; furthermore, the properties and reactions of molecules depend on the properties and interactions of the atoms in the molecules. Hence, to study the human body as a complex organization of molecules that undergoes a wide array of interrelated chemical reactions, we should begin by asking one of the most basic questions about any system of molecules: What sort of atoms does the system contain? The complete answer to this question will have two main parts: 1) what elements do the atoms represent, and 2) what interactions are found between the atoms (because the properties of a given atom can be altered by interactions with other atoms).

Hence, our discussion of the human body as a chemical system begins by answering the question, "What type of atoms does the body contain?" Of the more than 100 chemical elements known to scientists today, only a relatively small number of these elements are found in the human body. In fact, only 24 different elements are thought to be essential to the human body. (Other elements, such as mercury, are sometimes found in the body, but do not perform any known essential or beneficial function.) The largest elemental components of the body, by mass, are oxygen (65%), carbon (18%), hydrogen (10%), and nitrogen (3%). The other elements in the body, such as calcium, phosphorus, iron, and copper, are known to physiologists as mineral elements and trace elements. Although these elements make up a much smaller percentage of the mass of the body than oxygen, carbon, hydrogen, and nitrogen, the mineral and trace elements are vital to the body's proper functioning. These elements must be present in the body in the proper amounts, and they must be available to react with other elements to form critical molecules and participate in important chemical reactions. In this tutorial, we will describe the importance of one essential trace element in the body, iron. Although iron comprises only 0.008% of the body's mass (approximately 6 g for a 160-lb (75-kg) adult male), we cannot live without this important element in our bodies.


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This page created by Matt Traverso, Washington University in St Louis.
© 2004, Washington University.
Materials and Information present may be reproduced for educational purposes only.

Revised: 2004-08-08