pack 23a - blood glucose control Flashcards
(14 cards)
what is homeostasis
the maintenance of a constant internal environment despite changes in the external environment.
blood pH
- the pH of blood is between 7.35-7.45
- if blood pH is too high or too low enzymes may become denatured
- the hydrogen bonds can be broken
- tertiary structure changes
- the active site changes shape
- the substrate no longer fits
- enzyme-substrate complexes cannot be formed
core body temperature
- if core body temperature is too high
- hydrogen bonds break
- tertiary structure changes
- the active site changes shape
- the substrate no longer fits
- enzyme-substrate complexes cannot be formed
negative feedback
a change from a set point is detected and this brings about physiological mechanisms to return to the set point
positive feedback
any change away from the norm creates more change
why is high blood glucose concentration (hyperglycaemia) potentially dangerous
-water potential of blood decreases
- water enters the blood from cells
- organs may become dehydrated
- blood pressure will increase, potentially leading to cardiovascular disease
why is low blood glucose concentration (hypoglycaemia) potentially dangerous
- cells may not have enough glucose to maintain respiration rates
- water potential of blood increases
- water leaves blood and enters cells
- organs may swell up resulting in damage
- blood pressure decreases causing fainting
the role of the pancreas - blood glucose
receptors in the islets of Langerhans in the pancreas detect changes in the blood glucose concentrations
increase in blood glucose
- receptors on b cells in the islets of Langerhans detect the increase
- b cells secrete insulin into the blood steam
- insulin binds to specific protein receptors o the membrane of target cells (liver and muscle cells)
this causes:
- an increase in the uptake of glucose by cells. by causing more channel proteins to be inserted into the cell membrane which increase the permeability of the membrane for glucose
- glycogenesis which converts glucose to glycogen in the liver and muscle cells. glycogen can be stored.
- insulin activates enzymes which convert glucose to fats for storage in adipose tissue
- increasing respiration rates in cells
decrease in blood glucose
- receptors on alpha cells in the islets of Langerhans detect the decrease
- alpha cells release glucagon into the blood stream
- glucagon binds to specific protein receptors on the membranes of its target cells
this causes:
- glycogenolysis - glucagon activates enzymes which catalyse the conversion of glycogen to glucose
- gluconeogenesis - glucagon also activates enzymes which stimulate the conversion of amino acids and glycerol to glucose
the role of adrenaline
- adrenaline is secreted from the adernal glands when blood glucose concentrations are low (stress and exercise)
- adrenaline binds to receptors on the cell membrane of liver cells
this results in increased blood glucose in two ways:
- activating an enzyme that causes the conversion of glycogen to glucose glycogenolysis
- inactivating an enzyme that synthesises glycogen from glucose
second messenger model
- adrenaline attaches to receptor site on liver cell
- activates the enzyme adenylate cyclase inside the membrane
- the activated adenylate cyclase converts ATP to cAMP
- this acts as a second messenger that activates the enzyme protein kinase A
- protein kinase A activates a chain of reactions that break down glycogen to glucose (glycogenolysis)
type one diabetes
cause:
- b cells do not produce insulin
effects:
- blood glucose concentrations rise and stay high for a long period of time
treatment:
- insulin injections - the amount must match glucose intake
not given orally because it is a protein and would be hydrolysed in the stomach
type two diabetes
cause:
- gradual loss in the responsiveness of target cells to insulin due to receptors abnormalities
- often linked to obesity, age, lack of exercise and poor diet
treatments
- managed by careful regulation of diets and exercise
- losing weight may be advised
