Module 6- Homeostasis

Question 1

Define homeostasis

Answer 1

Maintaining a constant internal environment

Question 2

Define negative feedback

Answer 2

A change to the normal level initiates a response which counteracts the change

Question 3

Blood glucose concentration too high

Answer 3

1. Alpha and beta cells detect a change in blood glucose level
2. Insulin released from Beta cells in iselt of langerhan in pancrease
3. Protein hormone travels in blood to target tissue on liver/ muscle cells
4. Insulin binds to specific and complementary surface receptors
5. Membrane becomes more permeable to glucose due to inclusion of more glucose channels and more channels opening
6. Glucose enters cells by facilitated diffusion, down concentration gradient
7. Glucose is stored at glycogen through an enzyme controlled reaction (glycogenesis)
8. Blood glucose level returns to optimum

Question 4

Blood glucose concentration too low

Answer 4

1. Alpha and beta cells detect a change in blood glucose level
2. Glucagon released from Alpha cells in iselt of langerhan in pancrease
3. Protein hormone travels in blood to target tissue on liver/ muscle cells
4. Glucagon binds to specific and complementary surface receptors
5. Adenylate cyclase activated and tertiary structure of active site changes to become complementary to ATP
6. ATP –> cAMP
7. cAMP binds to protein kinase and change tertiary structure active site to become complementary to glycogen
8. Glycogen –> glucose (glycogenolysis)
9. New glucose is formed via gluconeogenesis, when amino acids and glycerol are combined
10. This is an enzyme controlled, condensation reaction
11. Glucose exits cells by FD, down conc gradient
12. Blood glucose level return to optimum

Question 5

3 marks

Explain how normal mice prevented their blood glucose concentration falling when they had not eaten for 48 hours

Answer 5

• 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

Question 6

5 marks

How does maintaining a constant body temperature allow metabolic reactions in cells to proceed with maximum efficieny

Answer 6

1. Optimum temperature for enzymes is 37 C
2. Increase temp–> denatures enzymes (alters tertiary structure of active site so substrate can no longer bind)
3. Slower reactions
4. Lower temo–> less kinetic energy of molecules
5. Fewer enzyme- substrate complexes

Question 7

Type 2 diabetes

Answer 7

Receptors on liver/ muscle cells do not respond to insulin