Carbohydrates are molecules built from sugars. They can exist as simple, single sugar molecules (monosaccharides), or chains of two or more sugar molecules (disaccharides and polysaccharides). Carbohydrates are an important source of energy and structural material for organisms.

Carbohydrates can be represented by the stoichiometric formula Cm(H2O)n (where m could be different from n). In sugars such as glucose and fructose and their derivatives, n = m and the ratio of carbon to hydrogen to oxygen is 1:2:1. This formula also explains the origin of the term “carbohydrate”; which means hydrated or watered carbon. The components are carbon (“carbo”) and water (“hydrate”).

Carbohydrates are an essential part of a diet because they provide energy to the body. Most people are familiar with carbohydrates, especially when it comes to what we eat. For example, to lose weight, some individuals adhere to “low-carb” diets. Athletes, in contrast, often “carb-load” before important competitions to ensure that they have enough energy to compete at a high level. Grains, fruits, and vegetables are all natural sources of carbohydrates that can be used for energy. These foods consist of both soluble and insoluble carbohydrates; the insoluble part is known as fibre, which is mostly cellulose.


  • McMahon, L. Plants and society 5th Edition. Chapter 10: Human Nutrition. McGraw-Hill, 2008.