9.1.1 - Homeostasis and hormones in mammals

Question 1

What is homeostasis?

Answer 1

The maintenance of a constant internal environment.

Question 2

Why is homeostasis important?

Answer 2

Changes in pH and temperature can affect enzymes and therefore chemical reactions.
Changes in water potential can cause cells to potentially burst if water moves in by osmosis.

Question 3

Describe briefly the key steps in homeostasis?

Answer 3

1 - optimum where the reaction works best
2 - Receptor detects change from optimum
3 - coordinator Links the receptor and effector
4 - Effector is a muscle or gland which brings changes to return the system to the optimum

Question 4

What is negative feedback?

Answer 4

A system deviates from the optimum.
Change is detected by the receptor.
A change is then produced which returns the system back closer to the optimum.

Question 5

What is positive feedback?

Answer 5

A system deviates from the optimum.
Change is detected by the receptor.
A change is then produced which causes an even greater deviation from the optimum.

Question 6

What are hormones?
How do they travel?
Give an example of a protein hormone and a steroid hormone.

Answer 6

Organic chemicals produced in an endocrine gland.
The travel in the bloodstream.
Protein = insulin
Steroid = testosterone and oestrogen.

Question 7

Explain the importance of maintaining blood pH in homeostasis.

Answer 7

pH needs to be optimum for enzymes.
Too high pH denatures enzymes as disulphide bonds in the tertiary structure are broken.
Therefore substrate can’t bind.
Reactions slow down as less enzyme substrate complexes form.