Chemical Composition of the Human Body

Major Classes of Compounds in the Human Body

Most of the elements are found within compounds. Water and minerals are inorganic compounds. Organic compounds include fat, protein, carbohydrates, and nucleic acids.

• Water: Water is the most abundant chemical compound in living human cells, accounting for 65 percent to 90 percent of each cell. It's also present between cells. For example, blood and cerebrospinal fluid are mostly water.
• Fat: The percentage of fat varies from person to person, but even an obese person has more water than fat.
• Protein: In a lean male, the percentages of protein and water are comparable. It's about 16 percent by mass. Muscles, including the heart, contain a lot of muscle. Hair and fingernails are protein. Skin contains a large amount of protein, too.
• Minerals: Minerals account for about 6 percent of the body. They include saltsand metals. Common minerals include sodium, chlorine, calcium, potassium, and iron.
• Carbohydrates: Although humans use the sugar glucose as an energy source, there isn't that much of it free in the bloodstream at any given time. Sugar and other carbohydrates only account for about 1% of body mass.