F6 Receptors and signalling Flashcards
(52 cards)
examples of chemical messengers
- hormones
- growth factors
- neurotransmitters
- paracrine agents
simply describe hormones. site of secretion and effects
- secreted from site of synthesis in circulating blood (for long range communication)
- has short and long term effects
effect of growth factors
long term control of cell growth and differentiation
effect of neurotransmitters
fast chemical transmission at neuronal synapses
effect of paracrine agents
local control of cell behaviour in the immediate environment
explain relationship between adrenaline and noradrenaline
- adrenaline is a hormone and noradrenaline is neurotransmitter
- they work on the same set of adrenoceptors
common characteristics of receptors
- selective binding site for native hormone / transmitter
- act as molecular switches (inactive and active states)
- signal is amplified
common types of signal amplification
- second messenger (many molecules produced eg. cAMP)
- enzyme activity (catalytic: many molecules of substrate converted)
what are the 4 superfamilies of receptors?
- ligand-gated ion channels
- G protein coupled receptors
- catalytic receptors
- nuclear receptors
order the 4 types of receptors from fast to slow
- ligand-gated ion channels
- G protein coupled receptors
- catalytic receptors
- nuclear receptors
what are ligand-gated ion channels primarily responsible for?
- fast synaptic transmission
- eg. nicotinic receptors
describe signal amplification in terms of ligand-gated ion channels
- opening a single ion channel lets thousands of ions flow through
describe amplification in terms of G protein coupled receptors
- 1 receptor can activate many G proteins
- activated ‘effector’ proteins are often enzymes or ion channels
describe catalytic receptors and what happens when activated. give an example
- what are they activated by and what do they cause?
- activated by hormone binding
- causes enzyme activity
- Tyrosine Kinase receptors for growth factors eg. EGF
give an example of a nuclear receptor
- transcription factors
- eg. steroid hormones (oestrogen receptor (ER))
describe the process of transcription factor action
- ligands diffuse across membranes to intracellular receptors
- when receptors (transcription factors) are activated, they can translocate to the nucleus and bind to DNA to promote transcription
why can ligands diffuse across membranes to activate transcription factors?
they are lipophilic
how does the G protein coupled receptor system cause amplification?
- one receptor can activate many G proteins
- activated ‘effector’ proteins are often enzymes or ion channels
why does the G protein coupled receptor system have flexibility?
it’s a 3 stage system that offers variety in messengers recognised and cellular responses generated
what do GPCRs look like?
- 7 transmembrane domain helices
- 7 transmembrane receptors
- extracellular N terminus
- intercellular C terminus
- 3 extracellular loops (ECL), 3 intracellular loops (ICL)
how do GPCRs exhibit a wide diversity?
- 800 different GPCR proteins
- 7 transmembrane domain ‘template’ allows many types of binding site (receptors can be adapted for different binding sites)
NA action on arterioles in GIT (binding site and result)
- bind to alpha 1 adrenoceptor
- cause contraction
NA action on arterioles in skeletal muscle
- bind to beta 2 adrenoceptor
- cause relaxation
NA action on airway smooth muscle in bronchioles (binding site and result)
- bind to beta 2 adrenoceptor
- cause relaxation
