A patient is prescribed Tolvaptan, a selective antagonist that blocks the binding of antidiuretic hormone (ADH) to V2 V_2\,V2 receptors on the basolateral membrane of the collecting duct principal cells. Which of the following correctly describes the cellular response in the collecting duct and the resulting effect on urine composition?
The density of apical aquaporin-2 channels decreases, resulting in a lower urine osmolarity.
The density of apical aquaporin-2 channels decreases, resulting in a higher urine osmolarity.
The density of apical aquaporin-2 channels increases, resulting in a lower urine osmolarity.
The density of apical aquaporin-2 channels increases, resulting in a higher urine osmolarity.
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.