Figure 3

Glucose-stimulated insulin release from a pancreatic β-cell. Exogenous glucose is taken up by GLUT2 and undergoes glycolysis inside the cell. Elevated adenosine triphosphate (ATP) levels alter the ATP/ADP ratio, which in turn leads to the closure of ATP-sensitive K⁺-channels. The subsequent membrane depolarization opens voltage-dependent Ca²⁺-channels in response to increasing intracellular calcium levels, which eventually trigger insulin secretion following vesicle fusion with the membrane.