6.4.2 Blood Glucose Concerntration

• Factors Influencing Blood Glucose Concentration:

  • Diet
  • Exercise 
  • Insulin
  • Glucagon
  • Adrenaline
• -genesis = to make
• -lysis = to break down
• Glycogenesis → excess glucose is converted into glycogen in the liver; [bg] is too high
• Glycogenolysis → glycogen is broken down into glucose in the liver; [bg] is too low
• Gluconeogenesis → glucose is formed from non-carbohydrates (eg amino acids & glycerol) in the liver; [bg] is low despite glycogenolysis
• Insulin = hormone secreted when beta cells in Islets of Langerhans (pancreas) detect the [bg] is too high
• Insulin Action

  1. Insulin attaches to receptors on target cells. The binding changes the tertiary structure of channel proteins so more glucose is absorbed into the cells by facilitated diffusion
  2. More protein carriers are incorporated into the membranes so even more glucose is absorbed form the blood into cells
  3. Glycogenesis occurs which is catalysed by activating enzymes
• Glucagon = a hormone produced in the pancreas in response to low glucose levels
• Glucagon Action

  1. Glucagon attaches to receptors on the surface of target cells 
  2. This stimulates adenylate cyclase to convert ATP into cyclic AMP (cAMP)
  3. cAMP activates the enzyme protein kinase which hydrolyses glycogen into glucose (glycogenolysis)
• Glucagon action can also activate enzymes for gluconeogenesis
• • cAMP acts as a second messenger
• Second Messenger Model → molecules inside as cell transmit signals intracellularly due to the binding of an extracellular molecule to a receptor
• Adrenaline = a hormone released from the adrenal gland when blood glucose concentration is too low
• Adrenaline Action

  1. Adrenaline attaches to receptors on the surface of target cells
  2. This causes a G protein to be activated and to convert ATP to cAMP
  3. cAMP activates an enzyme that hydrolyses glycogen to glucose (glycogenolysis)
• Type 1

  • Body is unable to produce insulin
  • Starts in childhood; inherited/genetic
  • Most often the result of an autoimmune disease where beta cells are attacked by antibodies
  • Treatment = insulin injections
• Type 2

  • Receptors on target cells lose responsiveness to insulin/insulin resistance
  • Usually develops in adulthood due to obesity & poor diet
  • Treatment = regulating uptake of carbohydrates, increasing exercise, insulin injections