Describe how negative feedback is used to control blood glucose concentration (6 marks)

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Throughout your answer to this question make sure that you are cramming as much key language into it as possible! Phrases like 'islets of Langerhans', 'beta/alpha cells', and 'transporter proteins' will all help you towards a valuable QWC mark.

Don't forget the technical names for the processes either! The words may seem long and intimidating but they can be broken down into easy chunks! 'Genesis' means 'to create', so glycogenesis is creating glycogen and gluconeogenesis is creating new glucose; 'lysis' means 'to destroy' so glycogenolysis is breaking up glycogen into glucose.

You have a choice about how you answer this one. You could talk about what happens when blood glucose is too high, and then talk about what happens when blood glucose is too low. On the other hand, you could just go into depth about one of these scenarios - if you do this, make sure you mention how the levels of BOTH insulin and glucagon change (ie. when blood glucose is high, insulin levels increase AND glucagon levels decrease).

Here's an example of how to nail all six marks:

'If blood glucose concentration becomes very high, glucose will diffuse into beta cells in the islets of Langerhans in the pancreas. This will cause calcium ion channels to open, stimulating the release of insulin into the blood by exocytosis. Also, the release of glucagon by alpha cells is supressed by the presense of glucose. Insulin is transported through the blood. Liver and muscle cells have receptors on their cell surface membranes that are complimentary in shape to insulin. When insulin binds to these receptors it stimulates vesicles containing glucose transporter proteins to merge with the cell membrane, allowing glucose to diffuse into the cell. This glucose is then phosphorylated and converted into glycogen by glycogenesis, for its energy to be stored. This causes the level of glucose in the blood to decrease back to normal levels.'

Matt H. A Level Biology tutor, GCSE Biology tutor, 13 plus  Science t...

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