Glucagon has a role in the maintenance of blood glucose concentration. Fig. 10.1 shows the relationship between blood glucose concentration and blood glucagon concentration, measured over 90 minutes in a healthy person. The person did not have any food in the three hours before the measurements were taken. [Figure 10.1]

1. (a)Explain the relationship shown in Fig. 10.1.[4]
2. (b)The passage below outlines cell signalling. Complete the passage by using the most appropriate scientific terms. Cells need to interact with their environment and other cells around them. This is called cell signalling. Cells in mammals are involved in a complex system of communication with each other. For example, liver cells detect signals using receptors in their cell surface membranes. Glucagon binds to the receptors because its shape is _______________, leading to stimulation of the enzyme _______________ _______________, leading to stimulation of the enzyme _______________.[3]

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