Monosaccharides & Polysaccharides


Each macronutrient in your diet breaks down into a smaller component. For example, proteins are broken down into amino acids, while carbohydrates break down into glucose molecules. The single unit for a glucose molecule is called a monosaccharide. When monosaccharides link together, the molecule is called a polysaccharide. Knowing how each of these molecules fits into your daily diet can help you get a mix of carbohydrates in your diet.

Basic Components

Monosaccharides and polysaccharides are both composed of one atom of carbon, two atoms of hydrogen and one atom of oxygen. Monosaccharides have only these four atoms present, while polysaccharides represent a string of monosaccharides bonded together. Because two bonded monosaccharides form a disaccharide, polysaccharides must have three monosaccharides or more. Physicians and chemists can use a test called Benedict’s Test for Reducing Sugars to indicate the presence of monosaccharides or polysaccharides in your foods.


Monosaccharides are simple sugars and can be present alongside polysaccharides in foods. An example of a food that contains both mono- and polysaccharides is the apple. The polysaccharide starch is present in the outer portion of the apple. As the apple matures, the inner portion turns from starch to simple monosaccharide sugars. Starch is the major energy storage source in plants. This is why eating an apple before it's ripe can keep the apple from tasting as sweet as it normally does. The outer skin of the apple is also a polysaccharide known as cellulose, which gives the apple a crunchy, fibrous texture. Monosaccharides are present in glucose-containing foods, such as honey and candy, which can provide a fast energy source for your body.


Your body is constantly breaking down the nutrients in your diet into smaller molecules that your cells can use. Polysaccharides are no exception, and the body must break them down into their monosaccharide components before they can be digested. This means that monosaccharide-containing foods will give you energy faster than polysaccharides because the body takes longer to break them down.


Polysaccharides are found in greater numbers in your foods than monosaccharides are. This is because polysaccharides provide structure and energy to plants, which are two important functions for human life. However, monosaccharides come together in the form of disaccharides to form lactose, a common sugar found in milk and sucrose -- also known as table sugar.


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