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How are carbohydrates stored and used by cells?
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Biochemistry
In biochemistry, researchers study the chemical substances and processes that occur in living organisms and cells. In particular, various processes by which cells gain energy, such as epinephrine-stimulated cAMP synthesis, have been deduced through the study of biochemistry.
Cells store and utilize carbohydrates as a primary energy reserve, though the specific storage molecules differ between organisms.1
Storage of Carbohydrates
- Animals: Cells store carbohydrates as glycogen, a highly branched polysaccharide of glucose units. It is found in high concentrations in the liver and muscle cells. The liver acts as a central reservoir, storing glycogen to maintain blood glucose levels, while muscle tissue maintains its own stores for local energy needs during activity.123
- Plants: Plants store energy as starch, which consists of amylose and amylopectin. These are stored in specialized parenchymatous cells within structures like tubers and seeds.1
Utilization by Cells
When energy is required, these storage polysaccharides are broken down into glucose units.14
* Mobilization: Enzymes such as glycogen phosphorylase release glucose from glycogen as glucose 1-phosphate, which is then converted to glucose 6-phosphate.4
* Energy Production: Through cellular respiration—specifically glycolysis and the TCA cycle—cells degrade glucose to capture chemical energy in the form of ATP. This process is tightly regulated by the cell's energy state, where levels of ATP, ADP, and AMP signal whether to store glucose or catabolize it for immediate energy.35