Control of blood glucose

• Factors which influence blood glucose concentration


  • Ingesting food or drinks which contain carbohydrates - levels will increase
  • When doing exercises (glucose used in respiration) or you haven't eaten - levels will fall
• Ways glucose can enter the blood stream


  • Non-carbohydrate stores such as lipids, lactate and amino acids can be converted into glucose
  • Absorption of glucose through the gut following carbohydrate digestion
  • Hydrolysis of glycogen stores in the liver
• Control of blood glucose levels

  A negative feedback system
• Glycogenesis


  1. The making of glycogen

  2. Excess glucose is converted into glycogen when blood glucose levels are higher than normal

  3. Occurs in the liver
• Glycogenolysis


  1. The breakdown of glycogen

  2. Breakdown of glycogen back into glucose when blood glucose levels are lower than normal

  3. Occurs in liver
• Gluconeogenesis


  1. Creating glucose

  2. The process of creating glucose from non-carbohydrates stores in liver

  3. Occurs when blood glucose levels are too low but all the glycogen has been hydrolysed back into glucose
• Islets of Langerhans


  • Endocrine cells in pancreas
  • Release both the hormone glucagon and insulin
  • Contain Alpha and beta cells
• Beta cells


  • In pancreas on islets of Langerhans
  • Detect an increase in blood glucose levels
  • Release insulin into the blood stream
• How insulin lowers blood glucose levels

  1. Insulin attaches to receptors on the surface of target cells - liver cells

  2. Changes the tertiary structure of channel proteins which allows more glucose to be absorbed

  3. Also allows for protein channels to be incorporated into cell membranes so more glucose can be absorbed by target cells - liver cells

  4. Further activates enzymes which are involved in the conversion of glucose into glycogen - glycogenesis
• Alpha cells


  • In pancreas on islets of Langerhans
  • Detect a decrease in blood glucose levels
  • Release glucagon into the blood stream
• How glucagon increases blood glucose levels

  1. Attaches to receptors on the surface of target cells - liver cells

  2. Also activates enzymes (protein Kinase) involved in the conversion glycogen to glucose - Glycogenolysis

  3. Further activates enzymes involved in the conversion of glycerol and amino acids into glucose - gluconeogenesis
• Adrenaline


  • Secreted by adrenal glands
  • Secreted when blood glucose levels are too low
• How adrenaline increases blood glucose levels

  1. Attaches to receptors on the surface of target cells - liver cells

  2. Activates glycogenolysis BUT inhibits glucogenesis

  3. Causes a protein to be activated and convert ATP to cAMP

  4. cAMP activates enzyme which hydrolyses glycogen into glucose - glycogenolysis
• Glucagon binds to


  Glucagon receptors
• Adrenaline binds to


  Adrenaline receptors
• Once bound glucagon and Adrenaline causes


  1. Changes the shape of enzyme adenylate cyclase

  2. Activates it
• Once activated adenylate cyclase converts


  ATP into cyclic AMP - cAMP
• cAMP


  Acts as the second messengers
• cAMP activates


  Protein Kinase
• Protein Kinase


  Activates a chain of reactions which breakdown glycogen into glucose - glycogenolysis
• Diabetes


  Condition where blood glucose concentration can not be controlled naturally
• Causes of type I diabetes


  • Body not able to produce insulin
  • Starts in childhood
  • May be result of autoimmune disease where beta cells are attacked
• Treatment for type I diabetes

  • Injection of insulin - Insulin therapy
  • May use insulin pump to deliver insulin continuously
  • Eating regularly controlling simple carbohydrate intake
• Hypoglycaemia


  Dangerously low blood glucose level
• Hyperglycaemia


  Dangerously high blood glucose level
• Causes of type II diabetes


  • Later in life
  • Linked to obesity, lack of exercise and poor diet
  • B cells don't produce enough insulin or body doesn't respond to insulin
  • Insulin receptors on liver cells doesn't work
  • Don't take up enough glucose
  • Blood glucose concentration remains high
• Treatment of type II diabetes


  • Eating healthy
  • Balanced diet
  • Losing weight (if necessary)
  • Regular exercise
  • Glucose lowering medication