Glucose are termed glucans. Glucose is produced by plants through the photosynthesis using sunlight, water and carbon dioxide and can be used by all living organisms as an energy and carbon source. However, most glucose does not occur in its free form, but in the form of its polymers, i.e. lactose, sucrose, starch and others which are energy reserve substances, and cellulose and chitin, which are components of the cell wall in plants or fungi and arthropods, respectively. These polymers are degraded to glucose during food intake by animals, fungi and bacteria using enzymes. All animals are also able to produce
Glucose 6-phosphate precursors of DNA for growth and synthesis, G6P will also be dehydrogenated and enter the pentose phosphate pathway. If the cell needs energy or carbon skeletons for synthesis, then glucose 6-phosphate is targeted for glycolysis. Glucose 6-phosphate is first isomerized to fructose 6-phosphate by phosphoglucose isomerase. This reaction converts glucose 6-phosphate to fructose 6-phosphate in preparation for phosphorylation to fructose-1,6-bisphosphate. The addition of the 2nd phosphoryl group to produce fructose-1,6-bisphosphate is an irreversible step, and so is used to irreversibly target the glucose 6-phosphate breakdown to provide energy for ATP production via glycolysis. If blood glucose levels are high, the