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Lecture 11

BIO241 Lecture 11

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University of Toronto St. George
Darrel Desveaux

BIO241 Lecture 10 Cell Communication - How cells communicate with their extracellular environment - Developmental responses, e.g. stress, infections - Unicellular organisms sense signals in environment, e.g. high [nutrients] or stressful environments, to respond appropriately - Multicellular organisms require complex signalling networks that are regulated - E.g. plants are sessile and cannot move away from stress, cells must respond appropriate so it may survive - Receptor interact with extracellular signalling molecules or enter cell and become intracellular signal molecule, inducing intracellular communication from receptor to effector proteins that will carry out response - Effector proteins may be metabolic enzymes that alter metabolism, gene regulatory proteins, e.g. transcription factors to alter transcriptional response like a developmental change, or cytoskeletal proteins that effect that shape, polarity, movement of cells and interactions between other cells - regulation of growth and replication of cells o cancer is a misregulation o signals can be positive influencing proliferation (EGF and EFGR) o cancer cells are overexpressed or hyperactive proliferative, many signals overactive in cancer o death factors or anti-growth factors knocked out leads to cell proliferation o signals coming into cells to regulate - e.g. dictyostelium (slime mold) once stressed, alters morphology and cell starts to produce cAMP and aggregate towards highest [cAMP] by extending pseudopod (chemotaxis moving towards high [chemical]) to form slug, going from unicellular to multicellular then forms fruiting body and produces spores that allows it to disperse away to new, better environment with no stress o cells evolve to respond to cAMP o movement initiated and activated by cAMP, intracellular signalling cascade from receptors to cAMP o PH domain required for chemotaxis, localizes to area of cell closest to cAMP (polarization), reorganization of cells to highest [cAMP] to form pseudopod (seen with GFP) - cell surface receptors usually in plasma membrane bind to hydrophilic ligand o ion channel linked receptors: ligand-gated, found in the membrane, e.g. regulated by neurotransmitters
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