Natural fiber exoskeletons of insects and arthropods. In shells and exoskeletons, the chitin fibers contribute to their hierarchical structure. In nature, pure chitin (100% acetylation) does not exist. It instead exists as a copolymer with chitin's deacetylated derivative, chitosan. When the acetylized composition of the copolymer is over 50% acetylated it is chitin. This copolymer of chitin and chitosan is a random or block copolymer. Chitosan is a deacetylated derivative of chitin. When the acetylized composition of the copolymer is below 50% it is chitosan. Chitosan is a semicrystalline “polymer of β-(1-4)-2-amino-2-deoxy-D-glucose”. One difference between chitin and chitosan is that chitosan is
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