During periods of fasting, blood glucose levels drop, triggering the release of glucagon from α\alphaα-cells in the islets of Langerhans. Which of the following describes the correct intracellular cascade initiated by glucagon in liver cells to elevate blood glucose?
Glucagon binds to intracellular receptors, activating tyrosine kinase to convert cAMP into ATP. ATP activates protein kinase A, promoting glycogenesis and gluconeogenesis.
Glucagon binds to transmembrane receptors, activating tyrosine kinase to convert ATP into cyclic AMP (cAMP). cAMP activates protein phosphorylase, promoting glycogenesis and glycogenolysis.
Glucagon binds to transmembrane receptors, activating adenylate cyclase to convert ATP into cyclic AMP (cAMP). cAMP activates protein kinase A, promoting glycogenolysis and gluconeogenesis.
Glucagon binds to intracellular receptors, activating adenylate cyclase to convert cAMP into ATP. ATP activates glycogen phosphorylase, promoting glycogenolysis and glycogenesis.
22 exam-style questions on OCR GCSE Biology 3.3 Maintaining internal environments, covering 3.3.1 Importance of a constant internal environment, 3.3.2 The skin and body temperature, 3.3.3 Insulin and blood sugar, 3.3.4 Glucagon and blood sugar, 3.3.5 Type 1 and type 2 diabetes, 3.3.6 Osmotic changes in body fluids, 3.3.7 Kidneys and water balance, 3.3.8 Structure of the kidney and tubule, 3.3.9 ADH and kidney tubule permeability, and 3.3.10 Responses to temperature and osmotic challenges. Each one has a worked solution and a mark scheme showing where the marks go.