glucoregulation

• Hormones:

  • Protein molecules 
  • Produced by endocrine glands 
  • Secreted into blood and carried to target cells 
  • Target cells have complementary receptors to a specific hormone 
• Hormones:

  • Insulin
  • Glucagon 
  • Adrenaline 
  • Steroids like oestrogen 
• Hormones are released from cells via exocytosis. 

  • Transcription of the hormone synthesis gene 
  • Translation at the ribosome 
  • Stored in the RER 
  • Then transported in a vesicle to the membrane 
  • Fusing of vesicle to cell membrane and release of hormone using ATP 
• Hormone regulation:

  • Negative feedback 
  • Reaching equilibrium means a reduction in secretion of the hormone
• Endocrine gland secretes hormones directly into the blood. 
• Exocrine gland secretes digestive enzymes into the pancreatic duct. 
• Exocrine gland:

  • Pancreatic cells surround small tubules which drain into pancreatic duct 
  • Pancreatic juice is made of: 
  • Amylase 
  • Endopeptidase 
  • Lipase 
• Endocrine gland:

  • Cells in the centre of the tubules that secrete hormones directly into the bloodstream 
  • Alpha cell secrete glucagon 
  • Beta cells secrete insulin 
• Natural sources of blood glucose:

  • Directly from diet when carbohydrates are hydrolysed
  • Glycogenolysis - hydrolysis of glycogen 
  • Glucogenesis - production of new glucose from non-carb sources 
• Alpha cells and glucagon:

  • Alpha cells act as receptors 
  • They secrete glucagon when they detect a fall in blood glucose 
  • Glucagon binds to the glycoprotein receptors on liver cells only 
• Glucagon and liver:

  • An enzyme is activated that converts glycogen to glucose - this is glycogenolysis 
  • There is an increase in the conversion of amino acids and glycerol into glucose - this is gluconeogenesis 
• Insulin and beta cells:

  • Beta cells act as receptors 
  • They secrete insulin when a rise in blood glucose is detected 
  • Insulin binds to glycoprotein receptors on the cell surface of body cells except for red blood cells 
• When insulin binds to cells:

  • Glucose channel proteins allow glucose to enter cells 
  • Increased number of glucose channel proteins in cell membranes 
  • Vesicles that contain the channel proteins fuse to the cell membrane and present them on the surface 
• Effect of glucose channel proteins on membrane:

  • More glucose is absorbed into cells 
  • Increased rate of respiration in cells 
  • More glucose is used in respiration 
  • Activation of enzymes that convert glucose to glycogen (glycogenesis) and fat in liver and muscle cells  
• gluconeogeneis 


  conversion of glycerole to glucose
• glycogenesis 


  glucose to glycogen
• glycogenolysis 


  glycogen to glucose