Central role of glucose in carbohydrate metabolism
Answers
The final products of carbohydrate digestion in the alimentary tract are almost entirely glucose, fructose, and galactose—with glucose representing, on average, about 80 per cent of these. After absorption from the intestinal tract, much of the fructose and almost all the galactose are rapidly con- verted into glucose in the liver. Therefore, little fructose and galactose are present in the circulating bloodGlucose thus becomes the final common pathway for the transport of almost all carbohydrates to the tissue cells.
Various biochemical processes responsible for the metabolic formation, breakdown, and interconversion of carbohydrates in living organisms.
Carbohydrates are central to many essential metabolic pathways.[1] Plants synthesize carbohydrates from carbon dioxide and water through photosynthesis, allowing them to store energy absorbed from sunlight internally.[2] When animals and fungi consume plants, they use cellular respiration to break down these stored carbohydrates to make energy available to cells.[2] Both animals and plants temporarily store the released energy in the form of high energy molecules, such as ATP, for use in various cellular processes.[3]
Although humans consume a variety of carbohydrates, digestion breaks down complex carbohydrates into a few simple monomers (monosaccharides) for metabolism: glucose, fructose, and galactose.[4] Glucose constitutes about 80% of the products, and is the primary structure that is distributed to cells in the tissues, where it is broken down or stored as glycogen.[3][4] In aerobic respiration, the main form of cellular respiration used by humans, glucose and oxygen are metabolized to release energy, with carbon dioxide and water as byproducts.[2] Most of the fructose and galactose travel to the liver, where they can be converted to glucose.[4]
Some simple carbohydrates have their own enzymatic oxidation pathways, as do only a few of the more complex carbohydrates. The disaccharide lactose, for instance, requires the enzyme lactase to be broken into its monosaccharide components, glucose and galactose.