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The human body is a very complex set of systems that can withstand enormous challenges as well as accomplish dramatic feats. It can be described chemically, biologically, physically, and in terms of its functions. Chemically, the body is mostly water with additional elements including calcium, nitrogen, oxygen, sodium chloride, iron, phosphorus, potassium, trace minerals, and carbon. The human body is composed of a number of organic compounds that include carbohydrates, lipids, nucleic acids, and proteins.

The carbohydrates supply energy to the body's cells. The body is maintained by energy derived from chemical reactions with carbohydrates. Lipids are fats that store energy for future use. Some lipids are the material used by the body to make the living cells of the body. Nucleic acids supply cells with ...

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