Hormone receptors and signalling

Question 1

What does target cell activation depend on

Answer 1

HOrmone concentration
Numbers of receptors on target cell
Affinity of the receptors for the hormone

Question 2

How does termination of the signal occur

Answer 2

Degredation of the hormone

Inactivation of receptor or signalling inc. receptor regulation

Question 3

How does the target cell make sure it does not become over stimulated by hormones

Answer 3

Increase in conc of hormone means there is down regulation of receptors

does this by:

• Inactivation of receptors
• Inactivation of signalling molecules
• Sequestration of receptors to inside of cell
• Degredation of internalised receptors
• Decreased production of receptors

Question 4

How does the target cell make sure it maintains sensitivity

Answer 4

if there is a decrease in hormone conc, there is up-regulation of receptors

Does this by:

• Decreased inactivation of receptors and signalling proteins
• Decreased sequestration and degradation of internalised receptors
• Increased production of receptors

Question 5

What are the four receptor types (superfamilies)

Answer 5

Ligand-gated ion channels (for neurotransmitters)

G-protein-coupled receptors (for hormones and slow transmitters such as muscarinic)

Catalytic receptors- (Cytokine receptor)

Nucelar- regulate gene expression (steroid and thyroid hormones)

Question 6

How do hormones act at receptors and where do they act

Answer 6

Water soluble hormones -
amino acid based hormones except thyroid hormones.
–> Act on plasma membrane receptors and don’t enter cells

Lipid soluble hormones- steroid and thyroid hormones
–> Act on intracellular receptors that directly activate genes and they can enter cell

Question 7

Which receptors do hormones act via

Answer 7

G protein coupled receptors

Catalytic receptors

Nuclear (intracellular) receptors