Control of Insulin secretion
  1. The cells membranes of the β cells contain both calcium ion channels and potassium ion channels
  2. The potassium ion channels are normally open, the calcium ion channels are normally closed. Potassium ions diffuse out of the cell, making the inside more negative; at rest the potential difference across the cell membrane is about -70mV
  3. When glucose concentrations outside the cell are high, glucose molecules diffuse into the cell
  4. The glucose is quickly used in metabolism to produce ATP
  5. The extra ATP causes the potassium channels to close
  6. The potassium can no longer diffuse out and this alters the potential difference across the cell membrane - it becomes less negative inside.
  7. This change in potential difference opens the calcium ion channels
  8. Calcium ions enter the cell and cause the secretion of insulin by making the vesicles containing insulin to move to the cell surface membrane and fuse with it, releasing insulin by exocytosis

Regulation of Insulin levels.

Insulin brings about effects that reduce blood glucose concentration.


So there wasn’t a question on Chi Squared. Hardy Weinburg was their weapon of choice. 

Nitrogen cycle and an awful lot of ecology questions. 

The genetic stuff was nice though, and the 7 mark question on tissue culture. 

That 11 mark question on animal behaviour, why thank you OCR.

No brain, body plan or nervous system (apart from those 2 marks on the differences between the CNS and peripheral.)

Nothing huge on clones or mutations either. *sigh*

What might come up

Stress might. I’m not a mind-reader, (as much as the exam board want me to be, it seems) but these are the things I think might come up this time. 

To reiterate: LOWER = ACCEPT,    higher = reject.


It’s only a guess, so please don’t just ignore everything else in the book. 

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