Receptors and signalling Flashcards
what is a ligand?
A ligand is any molecule that binds to a receptor
what is an endogenous agonist?
A chemical mediator found in the body that bind to receptors to produce a response
what is an example of an endogenous agonist?
* An endogenous agonist is a substance that is naturally produced by the body and activates a specific receptor
acetylcholine, insulin or noradrenaline
what is divergence signalling?
A single signal can activate multiple pathways, leading to diverse cellular outcomes.
ONE INPUT, MULTUPLE OUTPUT.
what is convergence signalling?
multiple receptors on one cell ultimately converge to activate a response or pathway. MULTIPLE INPUT, ONE OUTPUT
This allows amplification where multiple signals converge onto aa common downstream effector leading to a stronger response.
what is a receptor?
they are macromolecular proteins. They are recognition sites for different chemical mediators
AND
proteins of a cell that bind a molecule which modulates some activity of the cell
what are the four receptor classes/ superfamilies?
ligand ion gated channel
G protein -coupled receptor
kinase-linked receptor
nuclear receptor
Why are Nuclear receptors also called
1. Cytoplasmic receptors
2. Intracellular receptors
- Because, rather than floating in the nucleus, it could be in the cytoplasm of the cell.
- Because it’s found in the cell rather than on the membrane.
Which chemical mediators use each receptor type?
(–>) = activated by
Nucelar receptors –> steroidal hormones
Kinase linked receptros –> Peptide hormones, cytokines
G protein coupled receptors –> Peptide hormones + most small molecule chemical mediators e.g. amino acid derived neurotransmitters
Ligand gated ion channel receptors –> most small molecule chemical mediators e.g. amino acid derived neurotransmitters
what type of mediators use ligand gated ion channels?
small molecule chemical mediators such as amino acid derived neurotransmitters
what type of mediators use g protein coupled receptors?
Proteins and small molecules chemical mediators such as amino acid derived neurotransmitters
what type of mediators use g protein coupled receptors?
Proteins and small molecules chemical mediators such as amino acid derived neurotransmitters
what type of mediator uses nuclear receptors?
steroid hormones such as oestrogen
what is signal transduction?
The process that turns extracellular signals into intracellular signals
What does nAChR stand for?
Nicotinic Acetylcholine Receptor
(It’s an excitatory ligand gated ion channel)
What are the properties of cell surface Receptors?
(Ionotropic / metabotropic / kinase linked)
- each has transmembrane spanning segments
- each possesses a ligand binding domain (usually extracellular)
- ligands are hydrophilic, i.e. they can not cross the cell membrane
Why are G protein coupled receptors called “metabotropic”?
It can influence a signalling cascade (metabolic reactions associating phosphates, etc) within the cell
Key ideas about G protein coupled receptors (GPCRs)?
Formed from a single transmembrane protein
Receptor protein spans the membrane 7 times (so 7 transmembrane domains TMD)
Its has 3 different sub units
–> alpha
–> beta
–> gamma
So its a heterotrimetric GTP-binding protein (G protein)
Key ideas about ligand gated ion channels?
Involve ion channels
Involved in Fast synaptic transmission
Endogenous agonists are fast classical neurotransmitters stored in synaptic vesicles
Composed of 3-5 subunits i.e. transmembrane proteins
Complex arranged to form central aqueous pore
Agonist binding –> causing channel to open
Channel closes when agonist is removed OR receptor enters a “desensitised” state
What are the 2 types of ligand gated ion channel receptors?
Excitatory
Inhibitory
