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A-Level Biology OCR A

Glucose K Insulin Blood Conc Open Cell Potential

When blood glucose is high, beta cells take up glucose, increase ATP, close K+ channels, depolarize, allow Ca2+ entry, and release insulin through exocytosis.

High blood glucose causes glucose entry into beta cells, increased ATP, closure of K+ channels, membrane depolarization, Ca2+ entry, and insulin release via exocytosis.

Front Describe how insulin is secreted by beta cells in response to a high blood glucose concentration.
Back Insulin secretion:
  • At normal blood glucose conc - K+ channels are open and K+ diffuse out of cell, inside has potential of -70mV
  • Blood glucose conc rises - glucose enters cell through glucose transporter
  • Glucose is metabolised in mitochondria, ATP produced
  • ATP binds to ATP-sensitive K+ channels and causes them to close 
  • K+ ions can no longer diffuse out of cell, potential difference increases to -30mV & membrane depolarises
  • Depolarisation causes voltage-gated Ca2+ channels to open
  • Ca2+ ions enter cell and cause secretory vesicles to release insulin by exocytosis

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