Homeostasis

Question 1

(a) (i) What is meant by homeostasis?

Answer 1

Maintaining a constant internal environment

Question 2

(ii) Giving one example, explain why homeostasis is important in mammals. (2)

Answer 2

1. Temperature / Ph

2. Optimum for enzymes/ effect of PH/ temperature on enzyme activity

Question 3

(a) Explain how the normal mice prevented their blood glucose concentration falling
when they had not eaten for 48 hours
(3)

Answer 3

1. Release of Glucagon
2. Leads to formation of glucose in liver (cells);
   Reject: glucagon breaks down glycogen, or any other
   biological molecule
3. from amino acids/ non - carbohydrates / fatty acids
   Accept: gluconeogenesis / references to glycogen as source
   of glucose

Question 4

Describe the role of the hormone glucagon in the control of blood sugar concentration (4)

Answer 4

1. Binds to (specific receptors)
2. On muscle/ liver cells
3. Activates enzymes
4. Hydrolysis of Glycogen
5. Faciliated diffusion of glucose out of liver cells ; increases blood
   glucose levels