Final answer:
Glucose forming glycogen is not energetically favorable under standard conditions and relies on ATP hydrolysis for energy. Glycogen serves as a storage form of glucose and releases glucose monomers when needed for energy production through glycolysis.
Step-by-step explanation:
Glycogen formation from glucose is energetically favoured due to the energetics of ATP and its role in cellular metabolism. However, the process of glucose forming glycogen is not energetically favorable under standard conditions and requires the input of energy. This energetic barrier is overcome in cells, which are open systems, because the process is coupled to ATP hydrolysis, which is an energetically favorable reaction. In this coupled reaction, the hydrolysis of ATP provides the necessary energy to add glucose units to glycogen.
When energy is needed, such as during periods without food or during exercise, glycogen is hydrolyzed into glucose 1-phosphate monomers (G-1-P), which are then converted into glucose 6-phosphate (G-6-P) and fed into the glycolytic pathway to produce ATP. This metabolic flexibility allows for the conservation of energy and the maintenance of blood sugar levels under various physiological conditions.