A.
B.
C.
D.
参考答案:
D
本题详细解析:
Insulin is released by β-cells in the islets of Langerhans in the pancreas. The insulin is released into the blood and carried all around the body, so all body cells are exposed to it. When insulin binds to receptors on body cells it causes an increased uptake of glucose by these cells. Insulin has an added effect on liver and muscle cells as it stimulates them to take up glucose and store it as the complex storage carbohydrate, glycogen. Choice D is therefore correct.
α-cells secrete glucagon, not insulin (Choice A). It is cells in the pancreas, not the liver (Choice B) that secrete insulin. Glucagon is secreted when blood glucose falls, and insulin brings about increased glucose uptake in most body cells, not just liver cells (Choices B and C).
