Unit 6 - 3.6.4 Principles of Homeostasis and negative feedback

Question 1

Describe what is meant by negative feedback.

Answer 1

Where a change triggers a response which reduces the effect of a change

Question 2

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

Answer 2

1. Body temperature is optimum temp for enzymes;
2. Excess heat denatures enzymes by altering the tertiary structure. This alters the shape of active site so the substrate cannot bind;
3. This slows the rate of reaction;
4. Too little heat reduces kinetic energy of molecules
5. So there are fewer collisions and therefore fewer Enzyme-Substrate complexes formed;

Question 3

What is homeostasis?

Answer 3

Maintaining a constant internal environment;

Question 4

Giving one example, explain why homeostasis is important in mammals.

Answer 4

A change in temperature or pH; Would move away from the optimum conditions for enzymes therefore change the tertiary structure of the enzyme and the shape of the active site so enzyme-substrate complexes would not form as easily.

OR

A change in water potential or blood glucose;
This would effect osmosis in cells; as a decrease in water potential of the blood would cause water to move out of the cells by osmosis;

Question 5

Explain how a large increase in a person’s body temperature can cause harm.

Answer 5

It would cause enzymes to denatured by breaking hydrogen bonds; Changing the tertiary structure and the shape of the active site.

Question 6

What is positive feedback?

Answer 6

Where an increase leads to an increase
or a decrease leads to a decrease

Question 7

The regulation of the formation of helper T cells by interferon gamma is an example of positive feedback.

Explain why it is an example of positive feedback.

Answer 7

1. Because it causes more helper T cells to form;
2. So more interferon (gamma) is produced by helper T cells;

Question 8

The secretion of osteocalcin (in an inactive form) by osteoblasts is controlled by positive feedback.

Use information from the diagram to explain why this is positive feedback.

Answer 8

1. Osteocalcin causes more insulin to be released;
2. More insulin then causes more osteocalcin to be released;