9.2 Chemical control in mammals

Question 1

what are hormones?

Answer 1

proteins secreted by endocrine glands and trasnported in bloodtsream. They have specific tertiary structure is only complementary to receptors on certain cells.

Question 2

outline the general stages involved in negative feedback

Answer 2

receptors detect deviation –> coordinator –> corrective mechanism by effector –> receptors detects that conditions have returned to normal

Question 3

suggest why seperate negative feedback mechanisms control fluctuations in different directions

Answer 3

provides more control, especially in cases of ‘overcorrection’ which would lead to a deviation in the opposite direction from the original one

Question 4

why is there a time lag between hormone production and response by an effector?

Answer 4

it takes time to:
- produce hormnone
- transport hormone in blood
- cause required change to the target protein

Question 5

what are the two main modes of action in hormones

Answer 5

● hormones attach to receptor sites and trigger the release of a second messenger (like cAMP) that activates specific enzymes in the cell
● hormones enter cells and bind directly to transcription factors

Question 6

why are there two modes of actions of hormones

Answer 6

because there are two types of hormone:
- amides/peptides (adrenaline) which interact with specific receptos on the outside of the cell surface membrane
- steroid (oestrogen) which can pass through the cell surface membrane and interact with specific receptos within the cytoplasm

Question 7

explain the mode of action of adrenaline

Answer 7

1. Hormone-receptor complex forms
2. conformational change to receptor activates G-protein
3. Activates adenylate cyclase, which converts ATP to cyclic AMP (cAMP)
4. cAMP activates protein kinase A pathway
5. Results in glycogenolysis

Question 8

exlain the mode of action of oestrogen

Answer 8

1. steroid hormone diffuses through cell membrane
2. forms hormone-receptor complex with ER α receptor in the cytoplasm
3. complex enters the nucleus and acts as a transcrption factor.

Question 9

what is a second messenger

eg

Answer 9

an additional molceule that is used to tigger a response when a hormone attatches to receptor sites on a target cell surface membrane. (amide/peptide hormones)

cAMP