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Mechanism of Insulin Secretion

  1. When the blood glucose concentration is normal, ATP-sensitive potassium channels are open. Potassium ions diffuse out of the beta cells. The inside of the cell is -70mV relative to the outside of the cell.
  2. When blood glucose concentrations rise glucose enters the cell by glucose transporters.
  3. Glucose is used in respiration inside the mitochondria leading to a rise in the amount of ATP.
  4. ATP binds to the ATP-sensitive potassium channels and they close.
  5. Potassium ions are no longer able to diffuse out of the cell. Depolarisation occurs as the potential difference rises to about -30mV
  6. Depolarisation causes voltage-gated calcium ion channels to open.
  7. The entry of calcium ions into the cell causes secretory vesicles to fuse with the membrane and release insulin by exocytosis.

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Specification: AQA Biology (7402), A-level, 3.6.4.2 Control of blood glucose concentration. Topic: Hormonal Communication.

Key terms in this lesson

promoter
A region of DNA, upstream of a gene, to which RNA polymerase and transcription factors bind to begin transcription.
operator
A region of DNA in an operon to which a repressor protein can bind, blocking RNA polymerase from transcribing the structural genes.
repressor protein
A protein that binds to an operator or promoter region of DNA and prevents RNA polymerase from transcribing a gene.

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