- Any of a group of organic compounds that includes sugars, starches, celluloses, and gums and serves as a major energy source in the diet of animals; they are produced by photosynthetic plants and contain only carbon, hydrogen, and oxygen, usually in the ratio 1:2:1.
- Any of a large class of organic compounds consisting of carbon, hydrogen, and oxygen, usually with twice as many hydrogen atoms as carbon or oxygen atoms. Carbohydrates are produced in green plants by photosynthesis and serve as a major energy source in animal diets. Sugars, starches, and cellulose are all carbohydrates.
Substances composed of long chains of oxygen, hydrogen, and carbon molecules. Sugar, starch, and cellulose are all carbohydrates. In the human body, carbohydrates play a major role in respiration; in plants, they are important in photosynthesis.