10. Receptors in Cell Signalling and Receptor Structure Flashcards
Describe the following signalling by secreted molecule processes: paracrine, endocrine and synaptic.
Paracrine = signal acts on the adjacent cell. Endocrine = signal travels in the blood to act on far away tissues. Synaptic = neurotransmitter released from nerve cell and acts on target cell that it synapses with.
What are some subdivision of signalling molecules?
Local chemical mediators, hormones and neurotransmitters.
Will hydrophobic or hydrophilic signalling molecules act on cell surface or intracellular receptors?
Hydrophilic signalling molecules act on cell surface receptors.
Hydrophobic signalling molecules act on intracellular receptors.
What is a receptor?
A molecule that recognises specifically a second molecule or family of molecules and which in response to ligand binding brings about regulation of a cellular process.
What is a ligand?
Any molecule that binds specifically to a receptor site. This could cause activation (agonist) or no activation (antagonists).
How does the affinity of ligand binding at receptor sites compare to binding of substrates and allosteric regulators to enzymes?
It is much higher.
How are receptors classified?
According to specific physiological signalling molecule recognised. Also sub-classified by affinity of a series of antagonists.
What is the difference between receptors and acceptors?
Receptors are silent at rest (when no ligand is bound), but agonist binding stimulates a biological response.
Acceptors operate in the absence of ligands, ligand binding alone doesn’t produce a response.
What are some common mechanisms to transduce an extracellular hydrophilic signal into an intracellular event?
Membrane-bound receptors with integral ion channels.
Membrane-bound receptors with integral enzyme activity.
Membrane-bound receptors which couple to effectors through transducing proteins.
Intracellular receptors.
What is the structure of classical ligand-gated ion channels?
N-terminus on the outside with the he binding domain. 4 transmembraneous domains. C-terminus is also on the outside of the membrane.
How does signalling via tyrosine kinase-linked receptors work?
A hormone binds to the extracellular binding sites and activates a protein kinase activity in the cytoplasmic domain of the receptor protein. This auto phosphorylated the tyrosine residues on the cytoplasmic domain of the receptor. Phosphorylated receptor tyrosine residues are recognised either by transducing proteins or directly by enzymes contains phosphotyrosine recognition site. The effector enzymes get activated allosteric ally and transduceto the message into an intracellular chemical event.
What is the structure of G-protein coupled receptors?
N-terminus on the outside of the membrane with the binding domain usually on outside too. There are 7 transmembraneous domains (the binding domain could be within here sometimes). The C-terminus is on the inside of the membrane and has the G-protein coupling domain.
How does G-protein coupling work?
The G-protein binds to the receptor and there is G-protein subunit dissociation where the subunits go to activate the next receptor. GDP is release and GTP binds to the G protein. The subunits produce a secondary messenger.
What are the components of intracellular receptors?
Transcription activating domain, inhibitory protein complex, hormone binding site, hinge region and DNA binding domain.
How can a big result occur from small amounts of binding?
Amplification.
