Monosaccharides are simple sugars that cannot be broken down any further. They are the basic element of carbohydrates which turns into energy for our bodies.  Monosaccharides are a class of sugar molecules which are important for those who study biochemistry. They often dissolve in water, are colorless, and will form a crystal-like solid. Not all monosaccharides are sweet to taste. Examples of monosaccharides are glucose or dextrose, fructose, and Galactose.

Glucose or dextrose is the most plentiful sugar. It is found mostly in plants and in algae during photosynthesis. The glucose is used during this process to make cellulose in walls of cells. Glucose is the essential source of energy in all organisms. The World Health Organization (WHO) lists glucose as one of the most important components needed for a healthy living body.

Fructose is the sugar found in plants and fruit. When dried it is white, odorless and sweet. It is found in honey, flowers, berries, tree fruits, and most root vegetables. Commercial fructose is usually processed from corn, beets or sugar cane. The high-fructose corn syrup that is used in many foods is a combination of fructose and glucose. Fructose is often added to processed foods to enhance the taste. Too much fructose has been linked to many health problems, including obesity and diabetes.   

Galactose means milk sugar. It can be found in dairy products, sugar beets, and avocados. Galactose is also found in mammal secretions and bodily fluids, like milk. During the process of lactation, glucose becomes galactose which then becomes lactose in the milk.

Fischer Projection

Fischer projection is a two or three-dimensional diagram of a group of atoms. A flat stick drawing of the molecule, which preserves information about chirality or mirrored image. Fischer projections were created by Emil Fischer in 1891 and are the common way of showing monosaccharide molecules.

Carbon skeleton bonds are shown as vertical and other bonds are horizontal. If you imagine the vertical bonds bending back into the page and the horizontal bond being forward out of the page, you can reconstruct the three-dimensional structure in your mind.

Study Aid

The Monosaccharide study aid can be used when studying biochemistry many ways. Some activities are easier with a partner. You can practice naming sugars before you reveal the correct name by making a random monosaccharide and covering the name with your hand. You can build a monosaccharide by selecting the correct type of sugar and making a chiral carbon atom. You can pick two monosaccharides from a metabolic pathway, select the name of the first sugar, and discover what structural changes you need to make to change it into the second sugar. After looking at the cyclic structures in your textbook, you can use the monosaccharide study aid to build the straight chain form.

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