Fig. 1 shows a simplified liver cell from a person who has not eaten since the previous evening. The person’s blood glucose concentration began to decrease ...
Question 1 Report
Fig. 1 shows a simplified liver cell from a person who has not eaten since the previous evening. The person’s blood glucose concentration began to decrease during the night. The liver stores carbohydrate as glycogen, shown as many small granules. A hormone released by the pancreas can cause the liver cell to break down glycogen and release glucose into the blood. This is one part of keeping the concentration of glucose available for brain cells and other body cells.
(a) What is the name of the stored carbohydrate shown by the granules labelled X? [1]
(b) When blood glucose concentration falls, give the name of the pancreatic hormone that acts on liver cells. [1]
(c) Describe what happens to glycogen in the liver cell after this hormone acts. [2]
(d) Explain how the response shown helps body cells during the night. [4]
Answer Details
(a) The carbohydrate stored in liver-cell granules is glycogen. It is a large storage carbohydrate that can be converted back to glucose when needed. [1]
(b) The pancreatic hormone released when blood glucose falls is glucagon. [1]
(c) Glucagon causes glycogen to be broken down to glucose [1]. The glucose is then released from the liver cell into the blood [1].
(d) During the night, no new glucose is being absorbed from food, so blood glucose concentration would otherwise fall [1]. Glucagon causes the liver to release glucose into the blood [1], which raises or maintains blood glucose concentration [1]. Cells, including brain cells, can therefore carry out respiration and release energy [1]. This is negative feedback because the response opposes the original fall in glucose concentration.
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