Explain6 marksChallenge
A researcher investigates glucagon signalling in hepatocytes. She adds a very low concentration of glucagon (10⁻¹¹ mol dm⁻³) to a culture of normal hepatocytes and measures the glucose released into the medium. Despite the low hormone concentration, a significant amount of glucose is released. She then repeats the experiment using hepatocytes with a non-functional G-protein that cannot be activated by the glucagon receptor. These mutant cells release very little glucose even when treated with a 1000-fold higher concentration of glucagon.
Explain how a small number of glucagon molecules can cause the release of a large amount of glucose from liver cells.