The mammalian body is made of essentially non-living matter that is constituted and organized into forms that can contain and maintain life. The matter is in form of chemical compounds known as the chemicals of life. A description of these chemicals constitutes what is known as the chemical basis of life. There are two classes of chemical compounds in the mammalian body namely: a) Organic compounds. These are compounds that contain the element carbon covalently bound to other elements especially hydrogen, oxygen and nitrogen. b) Inorganic compounds. These are various types of salts/electrolytes in the body. Organic compounds There are four main classes of organic compounds in the body and these are referred to as macromolecules or biomolecules. They are: Carbohydrates. These are energy rich compounds that are readily broken down to release energy that runs the body’s life processes. They are also known as the biological fuel molecules. Carbohydrates are made of the elements carbon, hydrogen and oxygen and are simply abbreviated as CHO. Carbohydrates are synthesized by plants through the process of photosynthesis. Animals acquire carbohydrates by feeding on plants. There are two subdivisions of carbohydrates in the body depending on complexity as explained below: a) Sugars Sugars are small carbohydrate molecules found in the diets and in the bodies of animals. Sugars are also known as saccharides. Some saccharides consist of a single sugar molecule and are known as monosaccharides. The most common and well known monosaccharide in the mammalian body is glucose. A few saccharides consist of two sugar units joined together and are known as disaccharides or double sugars. Examples of disaccharides in mammalian diets are sucrose (cane sugar), lactose (milk sugar) and maltose (a breakdown product of starch). b) Polysaccharides -These are large carbohydrate molecules consisting of large numbers of sugar molecules joined together. Examples of polysaccharides in animal diets are starch, glycogen and cellulose.