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In energy metabolism, glucose is the most important source of energy in all organisms. Glucose for metabolism is stored as a polymer, in plants mainly as amylose and amylopectin, and in animals as glycogen. Glucose circulates in the blood of animals as blood sugar.
Because the level of circulatory glucose is largely determined by the intake of dietary carbohydrates, diet controls major aspects of metabolism via insulin. [18] In humans, insulin is made by beta cells in the pancreas , fat is stored in adipose tissue cells, and glycogen is both stored and released as needed by liver cells.
Carbohydrate metabolism This page was last edited on 31 August 2024, at 13:18 (UTC) . Text is available under the Creative Commons Attribution-ShareAlike 4.0 License ; additional terms may apply.
Glycolysis is the metabolic pathway that converts glucose (C 6 H 12 O 6) into pyruvate and, in most organisms, occurs in the liquid part of cells (the cytosol). The free energy released in this process is used to form the high-energy molecules adenosine triphosphate (ATP) and reduced nicotinamide adenine dinucleotide (NADH). [ 1 ]
As soon as the glucose enters the cell, it is phosphorylated into glucose-6-phosphate in order to preserve the concentration gradient so glucose will continue to enter the cell. [7] Insulin also provides signals to several other body systems, and is the chief regulator of metabolic control in humans. [citation needed]
Starting with glucose, 1 ATP is used to donate a phosphate to glucose to produce glucose 6-phosphate. Glycogen can be converted into glucose 6-phosphate as well with the help of glycogen phosphorylase. During energy metabolism, glucose 6-phosphate becomes fructose 6-phosphate.
The metabolic response to a carbohydrate challenge is conveniently assessed by a postprandial glucose level drawn 2 hours after a meal or a glucose load. In addition, the glucose tolerance test, consisting of several timed measurements after a standardized amount of oral glucose intake, is used to aid in the diagnosis of diabetes .
Glycolysis results in the breakdown of glucose, but several reactions in the glycolysis pathway are reversible and participate in the re-synthesis of glucose (gluconeogenesis). [9] Glycolysis was the first metabolic pathway discovered: As glucose enters a cell, it is immediately phosphorylated by ATP to glucose 6-phosphate in the irreversible ...