This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': 'The bitter taste is mediated by the action of \nSelect and explain. \nA. Guanyl cyclase, B. G protein, C. Tyrosine kinase, D. Epithelial Na+ chain', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Sweet- G protein coupled increased in cAMP causing closure of K+ channels.\nSalt- Opening of amiloride sensitive Na+ channels\nSour- Increased intracellular H+ concentration causing closure of K+ channels\nBitter- G protein-coupled increase in intracellular Ca++ triggering neurotransmitter release.', 'role': 'assistant'}]