(a)[2]
State where, within the cell, insulin receptors are found and identify the type of biological molecule that makes up an insulin receptor.
(b)
Insulin increases the activity of the enzyme glycogen synthetase in liver cells. Fig. 7.1 shows the activity of glycogen synthetase in liver cells during the 210 seconds after glucose is injected into the bloodstream.
(b(i))[2]
Calculate the percentage increase in glycogen synthetase activity from $90\ \text{s}$ to $180\ \text{s}$ after glucose had been injected into the blood. Show your working and give your answer to the nearest whole number.
(b(ii))[1]
Suggest the role of glycogen synthetase in controlling blood glucose concentration.