Exam q

• Describe how ultrafiltration occurs in a glomerulus.

  • High hydrostatic pressure
  • Water, glucose passes through small gaps in capillary endothelium
  • Passes through capillary basement membrane
• Increases thickness of medulla causes increase concentration of urine. Explain this pattern. (3)

  • Thicker medulla means longer loop of Henle
  • The longer the loop of Henle means increase in Na+ ion concentration in the medulla
  • More water is reabsorbed from the collecting duct by osmosis
• Explain the shape of the curve. (3)

  • Concentration rises in the descending limb as Na+ ions enter and water is lost
  • Concentration falls in ascending limb as Na+ ions actively removed
  • Water remains in ascending limb because its walls are impermeable to water

  
• Describe and Explain how the secretion of ADH affects urine produced by the Kidneys. (4)

  • Permeability of membrane increases
  • More water absorbed from collecting duct
  • Smaller volume of urine
  • Urine becomes more concentrated
• Why does the cell volume of an osmoreceptor decrease when a person is dehydrated ? (2)

  • Water potential of blood will decrease
  • Water moves from osmorceptor into blood by osmosis
• Explain why glucose is found in the urine of a person with untreated diabetes, using knowledge of kidney

  • High concentration of glucose in the blood
  • Not all the glucose is reabsorbed at the PCT
  • Co-transport proteins are working at maximum rate
• Describe the role of glucagon in gluconeogenesis (2)

  • Attaches to receptors on target cells and activates enzymes
  • Amino acids into glucose
• Explain how increasing a cell's sensitivity to insulin will lower the blood glucose concentration. (2)

  • More insulin binds to receptors
  • Stimulates uptake of glucose by transport proteins
• Explain how inhibiting adenylate cyclase may help to lower the blood glucose concentration (3)

  • Less ATP is converted into cAMP
  • Less kinase activated
  • Less glycogenolysis