A-LevelBiologyHomeostasis9700/42 · Oct/Nov 2020 · Q75 Marks

Insulin is transported around the body in the blood. The cells of the liver, muscle tissue and adipose (fat) tissue have receptors for insulin.

(a)State: • the precise cellular location of the insulin receptors • the type of biological molecule that forms an insulin receptor. location type of biological molecule[2]
(b)(i)Insulin stimulates the activity of the enzyme glycogen synthetase in liver cells. Fig. 7.1 shows the activity of glycogen synthetase in liver cells for 210 seconds after glucose has been injected into the bloodstream. [Figure 7.1] Calculate the percentage increase in glycogen synthetase activity between 90s and 180s after glucose was injected into the blood. Show your working and write your answer to the nearest whole number. answer %[2]
(b)(ii)Suggest the role of glycogen synthetase in the regulation of blood glucose concentration.[1]

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Mark scheme

Marking points from the official mark scheme (Oct/Nov 2020). The mark or mark type is shown in brackets.

[2] cell surface membrane / plasma membrane ;
[2] glycoprotein / protein / polypeptide ; R channel protein
[2] 19-5 / 5 ×100 or 14/5 ×100 ;
[2] 280(%);
[2] ecf - if candidate uses 18 instead of 19 then allow correct total of 260 for one mark
[1] (catalyses) glycogen production or decreases (blood glucose concentration);

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