Carbohydrates contain Carbon, hydrogen and oxygen.

Glucose is probably one of the most well known carbohydrates. The chemical equation for Glucose is C6H12O6 (6 carbon 12 hydrogen and 6 oxygen atoms). REMEMBER this as it is the product of photosynthesis and the key molecule used in cellular respiration.

Carbohydrate contain a lot of energy and their bonds are easily broken. Look at the reaction to the right. The heat and light produced by a single gummy bear, is due to  the bonds broken between the sugar molecules. This breaking down is a catabolic reaction (releases energy)

When you don’t use this energy, your body converts it to fat.

A single carbohydrate molecule is called a Monosaccharide. Examples are:

• Glucose
• Galactose
• Fructose

Notice the chemical equation for all three monosaccharides are C6H12O6.

When two monosaccharides are joined they form a Disaccharide. Examples of disaccharides are:

• Sucrose - Glucose + Fructose (found in fruits)
• Maltose - Glucose + Glucose (found in beer)
• Lactose - Glucose + Galactose (found in milk)

When carbohydrates bond with other molecules they create  a Glycosidic bond. This is a condensation reaction.

When two monosaccharides join, they loose a water molecule.

The animation to the right shows the formation of sucrose. Glucose (left) joins with fructose (right) to form Sucrose, loosing a water molecule in the process.

As seen in the photos above, starch has a spiral structure, while cellulose is layered and glycogen branches out.

Click here for an experiment on carbohydrates and enzymes

When 4 or more sugar molecules join they form a Polysaccharide. The most common Polysaccharides are:

Starch (energy storage molecule for plants)

Glycogen (energy storage molecule for animals).

Cellulose (building block of a plant’s cell wall)

Although Glycogen, Starch and cellulose are made from multiple glucose molecules the arrangement of the glucose molecules differ and thus, change the molecule.

Click here for a quiz on carbohydrates