control of blood glucose

• glycogenesis - converts glucose to glycogen in liver cells and muscle fibres - activated by hormone insulin and inhibited by glucagon and adrenaline
• glycogenolysis - converts glycogen to glucose - activated by hormone glucagon and adrenaline and inhibited by insulin
• glyconeogenisis - converts fats and proteins to glucose
• Cell signalling pathways and secondary messenger systems - role of glucagon in raising blood glucose levels: 

  1. Glucagon comes from tissue fluid
  2. Complementary cell surface receptor - glucagon binds (primary messenger) 
  3. Upon binding, adenylate cyclase enzyme is activated 
  4. Adenylate cyclase converts ATP to cAMP (secondary messenger) and x2 Pi 
  5. cAMP activates enzyme protein kinase 
  6. Protein kinase activates a different enzyme 
  7. The activated enzyme hydrolyses glycosidic bonds in glycogen - releasing glucose monomers  
  8. Facilitated diffusion of the glucose monomers into the bloodstream
• How does insulin lead to a decrease in blood sugar levels?

  insulin binds to receptors on liver cells , this causes more glucose carrier proteins to become active. Glucose can diffuse into the liver cells, reducing blood glucose concentration. Glycogenesis occurs in the liver cells And glucose is converted to glycogen
• How does adrenaline cause an increase in blood glucose levels?

  adrenaline binds to receptors on the cellmembrane of liver cells 

  this activates adenylate cyclase enzyme

  Adenylate cyclase converts ATP to cAMP, which then acts as a secondary messenger

  cAMP then activates Protein kinase which triggers glycogenolysis