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Topic 5 Extracellular Interactions.docx

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Kathleen Gilmour

Topic 5 - Extracellular Interactions Slide 1 -Cells are not in isolation they are part of a multi cellular organism and therefore they need to interact with the cells around them Slide 2 Plant cell wall produced by plant cell on outside of plasma membrane, and it serves to provide support (lack intermediate filaments), and it regulates permeability in some sense. Within matrix there are structural fibrils to provide mechanical strength: -Matrix mainly of hemicellulose and pectins, they attract water -Cellulose microfibrils provide strength to a cell wall Slide 3 Cellulose is a glucose polymer (long string of glucose), the cellulose microfibrils give strength to the cell wall, because they are imbeded in the pectin, and give the structural support Slide 4 -Cellulose is synthesized outside the cell -movement of cellulose is guided by microtubules so that youcan get patterns (networks) of cellulose Slide 5 Changing the pattern of microtubules changes the pattern of cell formation Slide 6 Problem with cell wall is it makes it difficult for the cells to communicate with each other. -cell walls are glued together with pectin -there is plasmodesmata (a hole through the cell wall, that acts a communicating gap, thats allows small molecules to get through (water, etc..) allows to cells joined together to get from one cell to the other Slide 7 -Animals dont have cell walls -variety of connections hold cells together: 1. Adhesive (anchoring) junctions hold the cells together 2.tight junctions form a seal in adjancent cells 3. gap junctions are used for commnicating with adjacent cells (similar to plasmodesmata/but diff. structure) Slide 8 -Plasmodesmata where just a whole in the cell wall -In Gap junctions you find specific integral membrane proteins that form a cell to cell connection, and thes proteins are called connexins, and they form a cytoplasmic connection between both cells (chemical & electrical communication) I.e. if bound to a nerve cell and 1 depolarizes, this will be passed on to neihgbouring cells Slide 9 -The gap junctions in the heart are important because it allows the heart beat to transfer to all other parts. the transmission of heart contractions is passed on through gap junctions Slide 10 -Tight junctions seal spaces. when you dont want things to go in between cell spaces. (i.e. uurine going through space of liver and into blodd) **:( bad -they allow different fluids to be separated from each other -found in skin so water doesnt escape cells to easily -tight junctions allow cells to become polarized Slide 11 -involve integral membrane proteins -in this case the protein protrudes on extracellular side of membrane, and forms connections on corresponding proteins from other cells -they do this in order to seal the connections between the cells -ridges formed of junctional proteins Slide 12 -Adhesive (anchoring) junctions prevents cells from falling apart 1.Adherens junctions work like velcro, you find long strips of them holding cell fairly well -strengthened by microfilaments 2.Desmosomes are more like buttons and they work to hold the cell really well at a specific point -strengthened by inte
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