cell signalling Flashcards
What is juxtacrine signalling?
Contact dependent
cells must touch
transmitted through membrane via protein and lipid essential to membrane
What is cell-matrix signalling?
Signals from the insoluble extracellular matrix
What are soluble signals?
Autocrine (intracrine) paracrine, endocrine
Describe autocrine and intracrine signals with examples
Autocrine= secreted and affect target cell itself via its own receptors
e.g interleukins
Intracrine= (version of autocrine) produced by and stay within target cells e.g steroid
Describe paracrine signalling with examples
signals target cells in the surroundings
local mediators released into the interstitial fluid: growth factors, cytokines
Describe endocrine signals
travel through circulation
high affinity
low conc
What are four ways of turning off a signal ?
- spontaneous breakdown
- enzymatic breakdown (cleavage of signal mol to inactive components)
- Reuptake
- receptor/ ligand internalisation
What are the three types of cell-cell contacts at organised junctions ?
- communicating junctions
- Anchoring junctions
- Occluding junctions
Describe communicating junctions
Animals = gap junctions plants = plasmodesmata ELECTROCHEMICAL SIGNALLING intercellular channels (made of 2 connexions) channels close at increased ca2+ conc
Describe anchoring junctions
Strength links between adherence junctions and desmosome
cadherins= ca2+ dependent molecules
Describe tight occluding junctions
Result in separation of lumen about an epithelium
Compartmentalise membrane and surround cell
Produce impermeable bonds between cells = limit paracellular permeability, maintain osmotic variance
What are two important transmembrane proteins in tight junctions ?
occluding and Claudia form bands at apex of epithelium cells, interact = make impermeable seal
What are two non specialised contacts ?
Notch
Selectins -mediate WBC adhesion
