Module 6- Homeostasis Flashcards
Define homeostasis
Maintaining a constant internal environment
Define negative feedback
A change to the normal level initiates a response which counteracts the change
Blood glucose concentration too high
- Alpha and beta cells detect a change in blood glucose level
- Insulin released from Beta cells in iselt of langerhan in pancrease
- Protein hormone travels in blood to target tissue on liver/ muscle cells
- Insulin binds to specific and complementary surface receptors
- Membrane becomes more permeable to glucose due to inclusion of more glucose channels and more channels opening
- Glucose enters cells by facilitated diffusion, down concentration gradient
- Glucose is stored at glycogen through an enzyme controlled reaction (glycogenesis)
- Blood glucose level returns to optimum
Blood glucose concentration too low
- Alpha and beta cells detect a change in blood glucose level
- Glucagon released from Alpha cells in iselt of langerhan in pancreas
- Protein hormone travels in blood to target tissue on liver/ muscle cells
- Glucagon binds to specific and complementary surface receptors
- Adenylate cyclase activated and tertiary structure of active site changes to become complementary to ATP
- ATP –> cAMP
- cAMP binds to protein kinase and change tertiary structure active site to become complementary to glycogen
- Glycogen –> glucose (glycogenolysis)
- New glucose is formed via gluconeogenesis, when amino acids and glycerol are combined
- This is an enzyme controlled, condensation reaction
- Glucose exits cells by FD, down conc gradient
- Blood glucose level return to optimum
3 marks
Explain how normal mice prevented their blood glucose concentration falling when they had not eaten for 48 hours
- Glucagon released from alpha cells in islet of langerhan of pancrease
- Leads to formation of glucose in liver cells
- Via gluconeogenesis when amino acids and glycerol are combined
5 marks
How does maintaining a constant body temperature allow metabolic reactions in cells to proceed with maximum efficieny
- Optimum temperature for enzymes is 37 C
- Increase temp–> denatures enzymes (alters tertiary structure of active site so substrate can no longer bind)
- Slower reactions
- Lower temo–> less kinetic energy of molecules
- Fewer enzyme- substrate complexes
Type 2 diabetes
Receptors on liver/ muscle cells do not respond to insulin
2 marks
A test for glucose in urine uses immobilised enzymes on a plastic test strip. One of these enzymes is glucose oxidase. Explain why the test strip detects glucose and no other substance.
- Active site has specific tertiary structure
- Only glucose can bind to form enzyme-substrate complexes
2 marks
Describe the role of glucagon in gluconeogenesis. Do not include in your answer details on the second messenger model of glucagon action.
- Attaches to receptors on target cells and activates enzymes
- Glycerol and amino acids combine to form glucose
2 marks
Metformin is a dru box g commonly used to treat type II diabetes. Metformin’s ability to lower the blood glucose concentration involves a number of mechanisms including:
* increasing a cell’s sensitivity to insulin
* inhibiting adenylate cyclase.
Explain how increasing a cell’s sensitivity to insulin will lower the blood glucose concentration.
- More insulin binds to specific and complementary surface receptors
- Stimulates uptake of glucose by channel/transport proteins
3 marks
Explain how inhibiting adenylate cyclase may help to lower the blood glucose concentration.
- Less ATP is converted to cAMP
- Less kinase is activated
- Less glycogen is converted to glucose/ Less glycogenolysis
During a glucose tolerance test the person remains at rest.
Why is it important that the person remains at rest?
- Movement uses muscles
- Movement increases rate of respiration
- Respiration uses glucose / respiration reduces blood glucose concentration
