1 - Overview - Gray Flashcards
Describe the OVERALL signalling pathway in UNICELLULAR organisms
- changes in environment eg external medium sensed and prokaryotes respond
- change detected at cell surface
- information relayed inside the cell
- expression of new genes designed to adapt to this new environment
Describe signalling in multicellular organisms eg how many genes expressed at once, why do we need signalling?
- 15-20% of all genes in cells expressed @ any one time in particular cell type
- controlling this expression enables cells/tissues to carry out a specific function
- coordination and control of gene expression ensures correct function of whole organism and prevents uncontrolled proliferation
- extracellular signalling allows signals to pass between cells that are microns-meters apart (& therefore control processes)
Name an organism that can be looked @ to study extracellular signalling
looking at Dictyostelium aggregation
- mid way between single celled and multicellular organism.
- eukaryote
- release of signalling molecules between the cells promotes aggregation
Overview the process of cell; cell signalling through extracellular signalling
1) signalling cell produces and releases the signalling molecule
2) detection and binding of signal to specific R on target cell
3) change in cellular behaviour triggered by L;R complex
4) removal of signal to terminate the cellular response
Name types of proteins that are associated with the plasma membrane and state how they play a role in signally.
- membrane bound, integral proteins
- facilitate signal transduction across membrane
- eg signal molecules that cannot directly diffuse through can reach the internal environment via carrier proteins, TM proteins, receptors
What are lipid rafts, why are they useful in signalling?
Draw a lipid raft
- more solid lipid micro environment can favour specific protein interactions and cause a signalling cascade
- properties of proteins eg no kinks in phospholipid tails/presence of cholesterol molecules enable the membrane to be > tightly packed together
343 - 1 word
What are gap junctions? What types of molecules can pass through these?
Draw a diagram to illustrate some features of these gap junctions
- allow direct communication between adjacent cells
- eg signalling molecules (Ca2+, cAMP) can pass directly between cells
- other small molecules can pass through tubes of protein called connexins which link cells together
- plants have plasmodesmata
What is signal transduction? What molecules can act as signals? What 2 types of signalling is there (think broadly)?
- conversion of an extracellular signal brings about their characteristic effects inside the target cells
- signal molecules can range from small eg Ca2+ to large aa eg auxin, acetylcholine or large peptides eg insulin
- INTER (between) /INTRA (within) signalling
Give definitions for ligands and receptor proteins
LIGANDS; eg hormones, growth factors, neurotransmitter. bind/activate specific receptors within or on cellular surface.
RECEPTORS; bind specific ligands, signal transduction across membrane -> internal change (eg across membrane OR into the nucleus)
Give 4 examples of the things RL complexes regulate
- metabolism through enzyme expression
- alterations of the cytoskeleton
- cellular growth/division/differentiation
- changes in gene expression in the nucleus
What are 2nd messengers? Give examples
- play in a role in generating intracellular response
- eg cAMP, Ca2+, IP3
Give the 4 types of distances that extracellular signalling operates over (give examples and draw diagrams of each)
ENDOCRINE; eg hormones in blood
PARACRINE; produced and act locally on nearby cells. responses can differ depending on amount of signal bound eg growth factors, neurotransmitters
AUTOCRINE; produced and act on the same cell. eg production of growth factors and tumour formation
PLASMA MEMBRANE ATTACHED PROTEINS; delta notch signalling. presence of delta leads to neuronal formation. eg differenting cells during development
