23A: Homeostasis - Blood Glucose Control Flashcards
Define Homeostasis:
- the maintenance of a constant internal environment (within certain limits) despite changes in the external environment
What is the normal pH of blood?
What is the core body temperature?
- 7.35-7.45
- 37
Describe what happens when the blood pH is subjected to change:
- hydrogen bonds will be broken
- tertiary structure changes shape
- active site changes shape
- substrate no longer fits
- enzyme-substrate complexes therefore cannot form
- so enzyme is denatured
Describe what happens when the core body temperature becomes too high:
- hydrogen bonds break
- tertiary structure changes shape
- active site changes shape
- substrate no longer fits
- enzyme-substrate complexes cannot be formed
- enzyme is denatured
Explain why high blood glucose concentration is potentially dangerous:
- Water potential of blood decreases
- Water enters the blood from cells & tissues by osmosis
- Organs, e.g. the brain, may become dehydrated – important metabolic reactions may not occur optimally.
- Blood pressure will increase, potentially leading to cardiovascular disease.
Explain why low blood glucose concentration is potentially dangerous:
- Cells may not have enough glucose to maintain respiration rates
- Water potential of blood increases
- Water leaves the blood and enters cells & tissues by osmosis
- Organs, e.g. the brain, may swell up resulting in damage
- Blood pressure will decrease, causing fainting
Describe what happens if Blood Glucose is too high:
- not the explanation
- receptors on beta cells in the Islets of Langerhans detect the increase
- these beta cells secrete insulin into the bloodstream
- insulin binds to specific receptors on the membrane of its target cells (usually liver + muscle cells)
Explain how the ____ cells cause a reduction in blood glucose concentration:
- increases the uptake of glucose by cells:
- glucose enters cells by facilitated diffusion using specific protein carriers
- insulin causes more channel proteins to be inserted into the cell membrane, which increases the permeability of the membrane for glucose - glycogenesis:
- insulin activates enzymes which convert glucose to glycogen in muscle + liver cells, to be stored - insulin activates enzymes to convert glucose to fats for storage in adipose tissue
- increases respiratory rates
Describe what happens if Blood Glucose is too low:
- receptors on alpha cells in the Islets of Langerhans detect a decrease in blood glucose concentration
- these alpha cells secrete glucagon
- glucagon binds to specific receptors on the membranes of its target cells (e.g liver + muscle cells)
Explain how the ____ cells cause an increase in blood glucose:
- Glycogenolysis: glucagon activates enzymes which catalyse the conversion of glycogen to glucose
- Gluconeogenesis: glucagon activates enzymes to catalyse the conversion of amino acids + glycerol to glucose
Describe the general hormone action:
- produced by endocrine glands
- transported in the blood to target cells in other organs of the body
- target cells have specific receptor proteins in the plasma membrane/cytoplasm
Describe the role of Adrenaline:
- adrenaline is secreted by adrenal glands when blood glucose concentrations are low (during stress and during exercise)
- adrenaline binds to specific receptors of the cell membrane of liver cells
How does Adrenaline lead to increases blood glucose concentrations?
- activates an enzyme that causes the conversion glycogen to glucose (glycogenolysis)
- inactivates an enzyme that synthesises glycogen from glucose (glycogenesis)
What hormones act via a second messenger?
Describe the Second Messenger Model:
- glucagon + adrenaline
- adrenaline approaches the receptor site of the liver cell
- adrenaline attaches to the receptor, and activates the enzyme adenylate cyclase
- activated adenylate cyclase converts ATP -> cyclic AMP (cAMP)
- cAMP acts as the second messenger that activates the enzyme protein kinase A
- protein kinase A activates a chain of reactions leading to the breaking down of glycogen to glucose
What is the cause of Type 1 Diabetes?
What are 2 effects?
What are some treatments?
Cause:
· β cells do not produce insulin.
· Maybe due to an autoimmune response where the body’s immune system destroys the β cells.
· Usually appears in childhood.
Effect:
- Hyperglycaemia: blood glucose concentrations rise and stay high for a long period of time after eating. This can be fatal.
- Kidneys cannot reabsorb all the glucose so some is excreted in the urine.
- Blood glucose concentrations must be monitored regularly, this can be done using a glucose biosensor.
- Insulin injections - the amount must match glucose intake.
- Management of diet and exercise to avoid hypoglycaemia (where glucose concentrations drop too low).
