Control of blood glucose concentration

• What detects an increase in blood glucose concentration?

  Beta cells in the Islets of Langerhans
• What do beta cells secrete when blood glucose concentration increases?

  Insulin
• Where is insulin secreted into?

  The blood
• What does insulin bind to on target cells?

  Complementary receptors on the cell surface membrane
• What happens when insulin binds to its receptors?

  Vesicles with glucose channel proteins fuse with the membrane
• How does glucose enter cells after insulin binds?

  By facilitated diffusion
• What process is activated in liver and muscle cells by insulin?

  Glycogenesis
• What is the purpose of glycogenesis in relation to glucose?

  To maintain a diffusion gradient
• What happens to blood glucose concentration after insulin secretion?

  It decreases back to the optimum
• What controls the stopping of insulin secretion?

  Negative feedback
• What is the overall process when blood glucose concentration increases?


  1. Beta cells detect increased glucose.
  2. Insulin is secreted into the blood.
  3. Insulin binds to receptors on target cells.
  4. Glucose channel proteins are activated.
  5. Glucose enters cells via facilitated diffusion.
  6. Glycogenesis occurs in liver and muscle cells.
  7. Blood glucose concentration decreases.
  8. Insulin secretion stops via negative feedback.
• What happens when blood glucose concentration decreases?

  Alpha cells secrete glucagon into the blood
• How do alpha cells respond to decreased blood glucose concentration?

  They detect the decrease and secrete glucagon
• What is the role of glucagon in the body?

  It binds to receptors on target cells
• What process is activated by glucagon to convert glycogen into glucose?

  Glycogenolysis
• What is the process called that converts glycerol and amino acids into glucose?

  Gluconeogenesis
• How does glucose enter the blood after glucagon secretion?

  By facilitated diffusion
• What happens to blood glucose concentration after glucagon is secreted?

  It increases back to the optimum
• What controls the secretion of glucagon?

  Negative feedback mechanism
• What are the key processes involved when blood glucose concentration decreases?

  • Alpha cells detect decrease
  • Secretion of glucagon
  • Glucagon binds to receptors
  • Activates glycogenolysis
  • Activates gluconeogenesis
  • Glucose enters blood via facilitated diffusion
  • Blood glucose concentration increases
  • Glucagon secretion stops via negative feedback
• Describe the second messenger model of increasing blood glucose concentration

  • Adrenaline/glucagon binds to receptors on the cell surface membrane of liver and muscle cells
  • This activates the adenylate cyclase enzyme which converts ATP to cyclic AMP (cAMP)
  • cAMP is the second messenger and binds to the protein kinase enzyme which changes its tertiary structure and activates it
  • Protein kinase hydrolyses glycogen to glucose which enters the blood by facilitated diffusion
• Describe type 1 diabetes

  Insulin dependent

  Cause: Insulin isnt produced as beta cells in the pancreas are destroyed by the immune system

  Control: Blood glucose concentration is monitored and insulin is administered regularly
• Describe type 2 diabetes

  Insulin independent

  Cause: Poor diet and obesity

  • Cells don't respond to insulin because receptors are damaged
  • Beta cells are damaged by over-production of insulin

  Control: Less sugar and fat, more exercise, drugs to increase insulin production or drugs to slow down glucose absorption