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UofT BIO230 Study Notes
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Final exam study notes for BIO230, taught by Dr. Yip in 2019
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BIO230 FINAL EXAM STUDY NOTES-understanding the molecular machinery involved in cell biology:
1. Cell + tissue spatial organization (membrane trafficking, cytoskeletal networks, cell adhesion)
2. Development of multicellular organisms (tissue morphogenesis, tissue patterning, stem cells)
3. Cell communication (cellular signalling, via small molecules, via protein modifications)
4. Control of cell numbers (cell cycle, programmed cell death, cancer)
1.1 MEMBRANE TRAFFICKING
-requires dynamic changes to plasma membrane
-secretory + endocytic pathways require(3): polarized trafficking routes, sorting stations, retrieval mechanisms
-3 membrane changes: fusion, invagination, budding (molecular machinery in cytoplasm for all 3)
Secretory Pathways:
-constitutive: unregulated membrane fusion, functions in all Eukaryotic cells
-regulated: membrane fusion requires hormone/neurotransmitter signal; specialized Eukaryotic cells
-provides extra plasma membrane during(3): cleavage furrow, phagocytosis, wound repair
Endocytic Pathways:
-endocytosed vesicle joins early endosome, then goes variety of places
-recycling: same side, transcytosis: opposite side
Ex. cholesterol endocytosis
-cholesterol binds to LDL which binds to LDL receptors, coated vesicle forms, receptors recycled
Regulating Transport Machinery: -work together for protein recruitment
-signalling lipids (PIP) - (de)phosphorylation of sugar group of inositol phospholipids
-small GTPases - active in GTP-bound state, inactive in GDP-bound state (Rabs 11, 5A, 7)
1.2 CYTOSKELETAL NETWORKS
Microtubules: heterodimer subunits(a and b), 13 protofilaments, bind GTP, motor proteins=dynein+kinesin
-nucleated by gamma-tubulin on minus ends (form centrosome matrix)
Ex. African cichild fish -colour determined by microtubule action
-black colour = increase cAMP, active kinesins+dyneins
-white colour = decrease cAMP, inhibit kinesins only
Actin Filaments: monomeric subunits, 2 protofilaments, bind ATP, motor protein=myosin
-nucleated by ARP complex, forms 2D polarized network (where cofilin + capping proteins are present)
-connected to ECM by integrins (TM heterodimers) + adaptor proteins
Polarized Movement: generates protrusive power, requires traction !!
-a stationary anchor (TM protein) reaches outside cell to push against floor (ECM)
, 1.3 CELL ADHESION
Epithelial Cell Structure:
1. Occluding (tight junctions) - claudins+occludins (TM); encircle apical end of each cell
2. Cell-cell anchoring (adherens+desmosomes) - cadherins+cadherin-family proteins; polarity landmark!
3. Channel-forming (gap junctions)
4. Cell-matrix (hemidesmosomes)
Ex. glucose transport - uses sodium/glucose symporter (apical) + passive glucose transport (basolateral)
Ex. Drosophila/vertebrate epithelial cells - Crumbs, Par3-Par6, scribble
2.1 TISSUE MORPHOGENESIS
-embryogenesis: multicellular development; fertilization(blastocyst) - before birth
1. Internalization of cells: forms 3 germ layers + gut tube (gastrulation)
-ingression/delamination - epithelial-mesenchymal transition; differentiated to less differentiated
-invagination/involution - microtubules elongate + apical actin contracts; form neural tube
2. Elongation of the embryo:
-convergent extension - outside of embryo becomes longer + thinner, convergence into dorsal midline
-cell division/shape change - (in Arabidopsis) orientation of cellulose microfibrils + turgor pressure
3. Fine repositioning of cells:
-cell migration - of whole cells (neurons) or cell extensions (commissural axons)
Ex. commissural neurons: attracted to ventral midline floor plate by netrin(DCC), repelled by
Slit(roundabout)+semaphorin
2.2 TISSUE PATTERNING
Cell Differentiation:
1. Direct lateral inhibition - creates pattern of isolated differentiated cells
Ex. Notch receptor inhibits cell specialization, delta activates Notch, Notch inhibits delta on same cell*
2. Induction by diffusible signals - creates bands of differentiated cells
3. Regulatory hierarchies - creates striping/segmental pattern
-asymmetric division - sister cells born different
Ex. defines germline in C. elegans - requires asymmetric determinants+proper spindle alignment
-symmetric division - sister cells initially the same, one changes from external signal
-morphogens - secreted molecules spread in gradient, concentrations can determine cell fate
Ex. “Organizer” tissues - dorsal lip tissue transplanted to ventral side of another embryo creates 2 dorsal sides
Ex. vertebrate limb - polarizing region of wing bud; more morphogen(Shh)=more digits
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