7- Cell:Cell communication, autocrine, juxtacrine, paracrine & endocrine signalling Flashcards
What is the essence of cell communication?
Molecules released by cells to induce change in behaviour of target cell
What is the relationship between Bobtail fish and Aliivibrio Fischeri?
Allivirbio fishceri have a symbiotic relationship with bobtail fish.
Lux genes are controlled by quorum sensing AHL auto inducer molecules.
A. fischeri synthesise AHL’s and at threshold concentration interact with lux r protein.
Lux r-AHL complex binds to the ‘lux box’ region of DNA causing luminescent genes to switch on.
A. fischeri have colonised the light organ and are bioluminescent but when free-living do not luminesce.
In what ways to quorum sensing molecules leave gram-positive and gram-negative bacteria differently?
Freely diffuse out of gram-negative bacteria
Actively transported out of gram-positive bacteria via ATP binding casette transporters
What are the 4 basic tenets of cell-signalling
Molecule released by cell
That cell and other local cells can respond, via receptor mediated signalling
Results in activation of transcription factors
There is a change in gene expression causing change in behaviour
What are the two broad categories of cell-signalling?
Contact-dependent - membrane- bound signalling molecule and receptor (juxtacrine)
Secreted molecules - paracrine, autocrine, endocrine, electrical signalling
What are three examples of juxtacrine signalling?
Gap junctions
Plasmodesmata
Cell-cell recognition
What are gap junctions?
Channels that directly connect one cell to another
How do gap junctions enable cardiomyocyte function? (cells responsible for hear contraction)
Autonomic nervous system ennervates pacemaker cells
Gap junctions facilitate initial wave of cations which allow depolarisation -> action potential -> muscle contraction.
Gap junctions connecting cells allow ions to travel through the musculature of the heart very rapidly and so the heart muscle can beat in rhythm i.e. at the same time
Synchronous depolarisation triggering muscle contraction (Ca2+ dependent)
What is this collective action called?
Functional Syncytium = wave of contraction that allows the tissue to work as a unit
What are plasmodesmata?
Gaps in the cell walls of plant cells that facilitate a continuous cytoplasm
What are two channels of plamsodesmata?
Tubule of ER - proteins inside ER pass through
Cytoplasmic sleeve - most things pass through -> continuous cytoplasm
What is one benefit and one disadvantage of plamsodesmata?
Advantage:
Allows nutrients and important biomolecules to be transported rapidly through the plant
Disadvantage:
Makes plants susceptible to infection, viruses can move between cells rapidly
What is the purpose of the variable aperture sizes of plasmodesmata?
Differently sized plasmodesmata are functionally linked.
Allows signalling by direct contact, ensuring only correct molecules and can pass through and get where they need to go.
How is Notch signalling pathway juxtacrine signalling?
Notch is a receptor molecule on cell surfaces and it interacts with ligands fixed on cell surfaces.
Therfeore it is contact dependent signalling
What important ligand in mammalian biology does Notch receptors interact with?
Delta
