Biological signalling molecules- Drug Targets

Question 1

paracrine signalling

Answer 1

signalling molecule secrete from the cell into the tissue. The molecule is then recognised by target cells within the tissue to produce a response

Question 2

endocrine signalling

Answer 2

the signalling molecule is released from the cell into the blood stream and goes to target cells

Question 3

what is a receptor

Answer 3

a molecule that recognises specifically a second molecule (ligand) or family of molecules and which in response to ligand binding brings about regulation of cellular process

Question 4

what is a ligand

Answer 4

any molecule that binds specifically to the receptor site

Question 5

what is the affinity for a ligand to a receptor like and why

Answer 5

ligands have a high affinity for receptor sites higher than that of substrates for enzymes as ligands are diluted in the bloodstream so the concentration is low therefore a high affinity is needed.

Question 6

how are receptor classified

Answer 6

classified according to:
-specific physiological signalling molecule (agonist) recognised

sub classified
-affinity (tightness of binding) of a series of antagonists

Question 7

what is the difference between a receptor and acceptor

Answer 7

receptors are silent at rest and agonist binding stimulates a biological response

acceptors operate in absence of a ligand and ligand binding alone produces no response

Question 8

what are the membrane bound receptors with integral ion channels

Answer 8

nAChR- Nicotinic acetylcholine recpetror

GABA- gamma amino butyric acid

glycine receptor

NMDA, AMPA and kainate- glutamate receptors

IP3 receptor

Question 9

membrane bound receptors with integral enzymatic activity

Answer 9

when silenced the catalytic domains re masked by their partner subunits

upon binding of agonists one or both of the subunits cause a conformational change which is trasnmitted against each other, thereby revealing the catalytic domauns which activates them on the cytoplasmic side

Question 10

example of membrane bound receptor with integral enzymatic activity

Answer 10

ANP receptor- linked directly to guanylyl cyclase

GTP TO cGMP

Question 11

Membrane bound receptors that signal through transducing proteins

Answer 11

coupled through GTP-binding regulatory proteins to enzymes or channels

adrenaline binding to beta-adenoreceptors activates the enxyme adenylyl cyclase (ATP cAMP) via G-protein, Gs

acetylcholine binding to M2 muscarinic acetylcholine receptors stimulates K+ channel opening via a different G-protein, Gi

Question 12

what activates the g protein

Answer 12

adrenaline binding to beta-adenoreceptors activates the enxyme adenylyl cyclase (ATP cAMP) via G-protein, Gs

Question 13

what inhibits the g protein

Answer 13

acetylcholine binding to M2 muscarinic acetylcholine receptors stimulates K+ channel opening via a different G-protein, Gi

Question 14

intracellular receptors

Answer 14

have a binding domain and a DNA-binding domain

the binding if hormones causes a conformational change in the receptor which dissociates the inhibitory complex revealing the DNA binding site