Blood Sugar Regulation

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Author:
camturnbull
ID:
270531
Filename:
Blood Sugar Regulation
Updated:
2014-04-14 15:09:42
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Biology Homeostasis camturnbull
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Description:
AQA BIOL5 Homeostasis
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  1. At what level must blood sugar be maintained?
    80mg/100ml
  2. What happens to cells that rise above the optimum blood sugar level?
    They become hypertonic and water is drawn out of them down a water potential gradient
  3. What happens to cells that fall below the optimum blood sugar level?
    The glycolysis stage of respiration is slowed down so brain activity is reduced
  4. Describe stage 1 of a glucose surplus response
    The change in blood glucose levels is detected by the beta cells in the islets of langerhans within the pancreas
  5. Describe stage 2 of a glucose surplus response
    The beta cells release insulin into the blood
  6. Describe stage 3 of a glucose surplus response
    The insulin binds to specific protein receptors in the membrane of liver cells
  7. Describe stage 4 of a glucose surplus response
    • Liver cells increase their permeability to glucose by transporting protein channels into the membrane meaning more glucose enters the cells 
    • Enzymes responsible for converting glucose into glycogen in a process of glycogenesis are also activated
  8. Describe stage 5 of a glucose surplus response
    Insulin also causes the liver to convert excess glucose into fats to be stored in adipose tissue under the skin
  9. Describe stage 1 of a glucose deficiency response
    The change in glucose levels is detected by alpha cells in the islets of langerhans within the pancreas
  10. Describe stage 2 of a glucose deficiency response
    Alpha cells release glucagon into the blood
  11. Describe stage 3 of a glucose deficiency response
    Glucagon binds to specific protein receptors in the membrane of liver cells
  12. Describe stage 4 of a glucose deficiency response
    • Liver cells activate the enzyme glycogen phosphorylase to hydrolyse the glycogen back into glucose 
    • This process is known as glycogenolysis
  13. Describe stage 5 of a glucose deficiency response
    • In times of stress or excitement, adrenaline from adrenal glands 
    • Adrenaline also stimulated glycogenolysis
  14. Describe stage 6 of a glucose deficiency response
    • If glycogen reserves are empty (due to fasting or otherwise) the liver cells produce new glycogen
    • This process is known as gluconeogenesis and is controlled by glucagon
  15. From where is new glucose synthesised by the liver?
    • Lactic acid from anaerobic respiration in muscles 
    • Glycerol from fatty acid breakdown 
    • Amino acid from body proteins
  16. Describe stage 1 of the second messenger model
    • The hormone (messenger no1) binds to a protein receptor on the membrane of the target cell to form a hormone receptor complex 
  17. Describe stage 2 of the second messenger model
    • A membrane bound enzyme know as adenylate cyclase is activated 
    • This enzyme converts many ATP molecules to cyclic AMP (messenger no2)
  18. Describe stage 3 of the second messenger model
    In the case of adrenaline and glucagon, each secondary messenger activates many enzymes that convert glycogen into glucose
  19. Describe stage 4 of the second messenger model
    A cascade reaction is formed with a single hormone resulting in a large number of activated enzymes
  20. What is diabetes?
    A disease caused by an inability to control blood glucose levels
  21. What effects does diabetes have on bodily cells
    • Glucose remains in the blood and is not absorbed by cells 
    • This means cells lack glucose for respiration leading to weight loss and fatigue 
    • The glucose in the blood lowers water potentials causing water to move out of cells down a water potential gradient via osmosis resulting in thirst and increased urine production 
    • Any urine produced contains glucose due to incomplete reabsorption in the kidneys
  22. What is type 1 diabetes
    • Insulin dependent diabetes
    • The pancreas is unable to produce insulin in response to high blood glucose levels
  23. How is type 1 diabetes treated?
    With regular injections of insulin
  24. What is type 2 diabetes?
    • Insulin independent diabetes 
    • Insulin is produced but the cells of the body fail to respond to it
  25. How is type 2 diabetes treated?
    • Reducing the amount of soluble sugar in the diet 
    • Eating carbohydrates in the form of insoluble starch which is absorbed more slowly as it needs to be digested first

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