CAIE A Level Biology 9700 · Homeostasis
When blood glucose concentration falls, the pancreas secretes glucagon. Glucagon binds to receptors on liver cells, initiating a signalling cascade that rapidly releases glucose from glycogen stores. Describe how this hormone signal is amplified through the intracellular signalling pathway, from glucagon binding to the activation of glycogen phosphorylase.
5 marks, so the mark scheme is looking for about 5 separate creditworthy points. Making the same point twice in different words earns it once.
Describe means: Say what happens or what something is like, in order and with detail. You are not being asked why. If there is data, quote it: name the trend, then give figures with units at the points where it changes.
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