Carbohydrate
Say it: kar-boh-HY-drayt
A carbohydrate is a sugar or a chain of sugars, such as starch or cellulose, built from carbon, hydrogen and oxygen and used for energy and structure.
Also: carbohydrates, carbs, saccharide
Definition
What is a carbohydrate?
Carbohydrates are one of the main classes of large biological molecules, alongside proteins, lipids and nucleic acids. Most have the general formula (CH2O)n, about one carbon atom for every water molecule, which is where the name comes from. The simplest are monosaccharides, single sugar units of three to seven carbons such as glucose, fructose, galactose and ribose. Two monosaccharides joined by a glycosidic bond, in a reaction that releases water, make a disaccharide, such as sucrose (table sugar), lactose (milk sugar) or maltose.
Long chains of sugar units are polysaccharides. Plants store energy as starch and animals as glycogen, mostly in the liver and muscles, while cellulose gives plant cell walls their strength and chitin forms insect exoskeletons and fungal cell walls. Small differences in how the units are linked matter a great deal: people can digest starch but not cellulose, which passes through the gut as dietary fiber.
In nutrition, carbohydrates are a macronutrient that the body breaks down to glucose, its main fuel for making ATP through glycolysis and cellular respiration.
Word parts
Where does the word “carbohydrate” come from?
- carbo-
- charcoal, carbonLatin carbo
- hydr-
- waterGreek hydōr
Practice it
Where you'll meet it
Quizzes that use it
- Macronutrients 101: Carbs, Proteins, and FatsFood Nutrition
- Clinical Nutrition: Diabetes and Metabolic SyndromeFood Nutrition
- Sports Nutrition and Performance OptimizationFood Nutrition
- Carbohydrate MetabolismBiochemistry
- Endocrine: Antidiabetic DrugsPharmacology
- Energy Metabolism and Caloric BalanceFood Nutrition
Related
Terms that go with it
- GlycolysisGlycolysis is the ten-step metabolic pathway that splits one glucose molecule into two pyruvate molecules, giving a net gain of two ATP.
- MacronutrientA macronutrient is a nutrient needed in large amounts, namely carbohydrate, protein or fat, which together supply energy and the raw materials for growth.
- MetabolismMetabolism is the full set of chemical reactions in a cell or organism, both those that break molecules down for energy and those that build them up.
- LipidA lipid is one of a varied group of biological molecules, including fats, oils, phospholipids, waxes and steroids, that do not dissolve in water.
- ProteinA protein is a large molecule made of one or more chains of amino acids, folded into a specific shape that determines its job in the body.
- Glycemic indexThe glycemic index is a scale up to 100 ranking carbohydrate foods by how much they raise blood glucose after eating, compared with the same amount of glucose.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
Last updated
Spotted a mistake? Tell us and we'll correct it.
Practice Biochemistry
Free biochemistry quizzes, with an explanation for every answer.
See the Quizzes