Fructose, also known as fruit sugar, levulose, and laevulose, is a simple monosaccharide which the body can use for energy. It is often found in combination with glucose as the disaccharide sucrose (table sugar), a readily transportable and mobilizable sugar that is stored in the cells of many plants, such as sugar beets and sugarcane. In animals, fructose may also be utilized as an energy source, and phosphate derivatives of fructose participate in carbohydrate metabolism.
Making up as much as 5 to 10 percent of any given fruit by weight, fructose is a sugar that naturally occures in low amounts in fruits and vegetables. Melons, berries, and honey are specially high in fructose. Bees gather nectar from flowers which contains sucrose. They then use an enzyme to hydrolyze or break apart the sucrose into its component parts of glucose and fructose.
Chemical Structure of Fructose
The molecule for organic fructose was first discovered in 1847 by Augustin-Pierre Dubrunfaut. The chemical structure of fructose, like all organic molecules, is carbon based. As a 6-carbon polyhydroxyketone, fructose has various structural forms based on acyclic and cyclic isomers. Fructose is a levorotatory monosaccharide (counterclockwise rotation of plane polarized light). Fructose’s chemical structure is very similar to glucose. Like glucose, fructose is a hexose (six-carbon) sugar, but it contains a keto group instead of an aldehyde group, making it a ketohexose. Fructose and glucose have the same empirical formula, but differ structurally (they are isomers of each other).
Fructose vs. Glucose
There are major differences in the human body breakdown of fructose and the more common simple sugar, glucose. Furctose must be converted by the liver into energy, fat, or glucose before it can be used by other organs. Conversely, Glucose is directally usable by virtually all tissues and organs and is the preffered energy source for the brain. Glucose and fructose breakdown in the liver both result in energy and fat production among other products. However, the glucose breakdown pathway is turned off when there is an accumulation of energy and fat, thereby preventing excess production. Fructose breakdown does not have this feedback mechanism, so energy and fat production depends solely on the presence of fructose. Therefore, a massive ingestion of fructose would result in an overwhelming production of energy and fat.
Appetite (the desire to eat food, felt as hunger) is regulated by a close interplay between the digestive track, adipose tissue, and the brain. The digestive track along with other organs send out hunger and satiety signals depending on the presence or absence of certain nutrients. One of those nutrients is glucose. After a meal, the elevation in blood glucose level will shut off the hunger signal and send a satiety signal to the brain. As a result, the individual would feel satiated. Conversely, fructose is less capable at regulating these signals. Therefore, while a high glucose meal will make an individual satisfied, an equal caloric high fructose meal would leave the individual still feeling hungry.
While fructose is generally regarded as safe, excessive consumption can lead to Hyperuricemia and increase your risk for diabetes and heart attacks. There are also certain digestive disorders that are associated with difficulty processing, or absorbing, fructose, such as Fructose Malabsorption, and Fructose Intolerance.
Fructose’s specific conformation (or structure) is responsible for its unique physical and chemical properties relative to glucose. Although the perception of sweetness depends on a variety of factors, such as concentration, pH, temperature, and individual taste buds, fructose is estimated to be approximately 1.2-1.8 times sweeter than glucose. Out of all the naturally occurring sugars and carbohydrates, fructose is the sweetest. Fructose is added to many foods and drinks because of its sweet flavor. Around 250,000 tonnes of crystalline fructose are produced annually.Tags:
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