Signalling And Receptors Flashcards
Give 2 types of intercellular signalling
Signalling by secreted molecules - signalling cell releases a signalling molecule that is recognised by a specific receptor on a target cell
Signalling by plasma membrane bound molecules - the target and signalling cells are adjacent
State and describe 3 methods that cells secrete molecules for signalling
Paracrine- mediated by local chemical mediator cells. This is for cells close to each other (within the same tissue)
Endocrine - signalling molecules are released into the blood stream and travel to cells in other tissues (distal)
Synaptic - nerve cells , specialised signalling between nerves and nerves or muscles. Signalling molecules are called neurotransmitters and cross a synapse
What are the 3 subdivisions of signalling molecules?
Relocalise chemical mediators
Hormones
Neurotransmitters
(Some can be both though)
Where can receptors be found ? And what are they in different places?
Cell surface receptors- on the plasma membrane. For hydrophilic (non lipid double) molecules that can’t pass through the membrane
Intracellular receptors-in the nucleus. For lipid soluble (small hydrophobic) molecules that can pass through membrane. Normally carried on a carrier protein like albumin.
What do molecules with intracelluar receptors do?
Work to activate or inhibite genes, work at a dna level
What is a receptor?
A molecule that recognises specifically a second molecule (ligand) or family of molecules and responds to ligand binding by bringing about regulation of a cellular process
What does a receptor do in an unbound state and why?
Receptor is silent (doing nothing). This stops random signalling.
What is a ligand?
A ligand is any molecule that binds specifically to a receptor site.
What are the different types of ligand?
Agonists - ligand binding causes activation of a receptor
Antagonist - ligand binding prevents activation (doesn’t deactivate but competitively inhibites so no signal is sent when bound)
What are the roles of receptors in cellular physiology?
Signalling
Neurotransmission
Cellular delivery (looking for nutrients)
Control of gene expression (intracelluar)
Cell adhesion
Release of calcium stores
Describe the binding affinity of receptors and enzymes comparatively.
Receptors have much lower concentrations of signalling molecule than enzymes have of substrate so receptors have a much higher affinity.
How are receptors classified?
Specific molecule they recognise (agonist)
Affinity to a series of antagonist
(Used more for when there are multiple receptors for one molecule so use affinity to sub classify).
What are the 2 types of acetylcholine receptors?
Give receptor type and agonist
Nicotinic which recognises nicotine
Muscarinic which recognises muscadine
What’s the difference between a receptor or acceptor?
Receptors- silent at rest. Agonist binding stimulates a biological response.
Acceptors- operate without ligand being bound.
Methods of signal transduction
How signalling molecules get through membranes
- Membrane-bound receptors with ion channels.
Fastest but difficult to maintain. - Membrane bound receptors with enzyme activity.
The receptor and effector are the same molecule. - Membrane bound receptors which couple to effector through translucent proteins.
- Intracelluar receptors.
What is the structure of a nicotinic acetylcholine receptor?
It is made of 5 subunits. It is a Chanel which a gated pore. Once acetylcholine binds there is a conformational change and the gate opens. It is selective for cations.
Describe the structure of the insulin receptor.
Made if both alpha an beta sections translated as a signal protein. Extracellualr space is the insulin binding domain. Then a transmembrane domain that goes through the membrane. Tyrosine kinase domain in the cytoplasm.
Describe membrane-bound receptors that signal through transducing proteins.
Coupled through g-protiejsbto enzymes or channels
Describe the structure of G-protein coupled receptors
Have 2 binding domains 1 outside the cell and 1 in the membrane, and a G-protein coupling domain. 7 rod like (alpha helix)structures in a circle around the binding domain.
Describe amplification in cellular signalling
1 signaling molecule could activate many GTP molecules. These could release many secondary messaging eras which all effect enzymes which could create much product. So at each level of transmission each molecule transmits to multiple other molecules.
Describe how inhibitory protein complexes can inhibit
When they bind to the receptor they cause a conformational change in the binding site (active site) meaning the signalling molecule can no longer be recognised. Steroid hormones can release inhibitory proteins activating the binding site if receptors again.
