Carbohydrates - A carbohydrate is an organic compound that is composed of atoms of Carbon, Hydrogen and Oxygen in a ratio of 1 carbon atom, 2 hydrogen atoms, and 1 oxygen atom. Some carbohydrates are relatively small molecules, the most important to us is glucose which has 6 carbon atoms. These simple sugars are called Monosaccharides

The primary function of carbohydrates is for short-term energy storage (sugars are for Energy). A secondary function is intermediate-term energy storage (as in starch for plants and glycogen for animals). Other carbohydrates are involved as structural components in cells, such as cellulose which is found in the cell walls of plants. Sugars are most often found in the form of a "RING". The sugar molecules in the image above and the sugars in the image below (Glc and Frc) are really the same molecules, just arranged differently. The Carbonyl (C=0) Carbon of the straight-chain form (above) has formed a bond with the next to last Carbon in the chain, forming a ring.

Hooking two monosaccharides together forms a more complex sugar, such as the union of glucose and fructose to give sucrose below (aka common table sugar). Compounds such as sucrose are called Disaccharides (two sugars). Both monosaccharides and disaccharides are soluble in water.

Here is a 3-D Disaccharide (chime)

Larger, more complex carbohydrates are formed by linking mny sugars together to form long or very long sugar chains called Polysaccharides. Because of their size, these are often times not soluble in water. Many biologically important compounds such as starches and cellulose are Polysaccharides. Starches are used by plants, and glycogen by animals, to store energy in their numerous carbon-hydrogen bonds, while cellulose is an important compound that adds strength and stiffness to a plant's cell wall.

There are several chemical tests that indicate the presence of carbohydrates. The two we examine below can also distinguish between Carbohydrates of different sizes.

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