Final answer:
The statement about Glucose-6-phosphate being a positive activator of glycogen phosphorylase in muscle but not in liver is false; it serves as an allosteric inhibitor in both tissues.
Step-by-step explanation:
The statement that Glucose-6-phosphate is a positive allosteric activator of glycogen phosphorylase in muscle, but not the liver is false. Glucose-6-phosphate is actually an allosteric inhibitor of glycogen phosphorylase in both muscle and liver tissues. In the liver, glucose-6-phosphate signals that there is ample glucose available, hence it inhibits the enzyme to prevent excess glucose release into the bloodstream. In muscle tissue, the inhibition of glycogen phosphorylase by glucose-6-phosphate ensures that glycogen is not broken down unnecessarily when there is sufficient glucose already available for muscle energy needs.
During glycolysis, hexokinase catalyzes the phosphorylation of glucose using ATP to form glucose-6-phosphate, which cannot cross the hydrophobic interior of the plasma membrane, effectively trapping it within the cell. Glycogen breakdown to glucose-1-phosphate and subsequent conversion to glucose-6-phosphate provides a source of glucose for ATP production within the cell. This process is important for maintaining blood sugar levels and meeting the energy demands of cells, particularly in muscle and liver cells.