6.1 Receptors in Cell Signalling

Question 0

Define ‘synaptic secretion’

Answer 0

Neurotransmitter is released from a pre-synaptic membrane to cause depolarisation

Question 1

Define ‘paracrine secretion’

Answer 1

Local mediators are released to effect cells close to them

Question 2

Define ‘endocrine secretion’

Answer 2

A hormone is released which travels in the bloodstream to have an effect at a different site.

Question 3

Define ‘receptor’

Answer 3

A molecule that recognises specifically a second molecule (ligand) and then on binding of the ligand produces a response.

Question 4

Define ‘ligand’

Answer 4

Any molecule that binds specifically to the receptor site to cause a response.

Question 5

What is the difference between an agonist and an antagonist?

Answer 5

Agonist: ligand which activates a receptor
Antagonist: ligand which binds to a receptor but does not produce a response.

Question 6

Define ‘acceptor’

Answer 6

Operates in the absence of a ligand. The ligand binding alone produces no response.

Question 7

Give an example of a membrane-bound receptor with an integral ion channel

Answer 7

Nicotinic acetylcholine receptor
GABA receptor
IP3 receptor

Question 8

Give an example of a membrane bound receptor with integral enzyme activity

Answer 8

ANP receptor- linked directly to cGMP

Growth factor receptors (eg. insulin)- linked directly to tyrosine kinase

Question 9

Give an example of a membrane-bound receptor which couples to effectors through transducing proteins

Answer 9

G-proteins
Adrenaline => beta-adrenoreceptors => adenyl cyclase

Acetylcholine => M2 receptors => K+ channels open

Question 10

Give an example of an intracellular receptor

Answer 10

Steroid hormones

Question 11

Explain the cascade effect

Answer 11

1 stimulus will stimulate several receptors which will activate many enzymes and so on, causing a large response.