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Cell Communities & Stem Cells Chapter 20 Key topics Structure & function of

Cell Communities & Stem Cells Chapter 20 Key topics Structure & function of -- the extracellular matrix -- cell junctions Tissue organization Properties of Stem cells. Questions in this chapter you should be able to answer: Chapter 20: all. Extracellular Matrix – I Plant cell wall

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Cell Communities & Stem Cells Chapter 20 Key topics Structure & function of

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  1. Cell Communities & Stem Cells Chapter 20 Key topics Structure & function of -- the extracellular matrix -- cell junctions Tissue organization Properties of Stem cells Questions in this chapter you should be able to answer: Chapter 20: all Cell Communities

  2. Extracellular Matrix – I Plant cell wall Composition cellulose hemicellulose lignin Organization Middle lamella 1O wall 2O wall Plasmadesmata Cell Communities

  3. How are cellulose fibers synthesized and oriented? Cellulose organization Cellulose synthase -- pushed forward Microtubule tracts – constrain movement Cellulose fibers Microtubules Cell Communities

  4. apical Animal tissue organization Epithelia Extracellular matrix -- Basal lamina -- Connective tissue Epithelia have polarity Tight junctions separate apical vs basal surfaces Cell Communities

  5. What are the 1O components of the ECM? Collagens Proteoglycans Collagens structure (Glc - X - Y) X often proline Y often hydroxyproline function organization many types Gelatin Scurvy Vitamine-C prolyl-hydroxylase  hydroxyproline Fibroblasts Collagen Cell Communities

  6. What are proteoglycans? Polysaccharide core (hyaluronate) + Protein linkers + GAG branches (glucoseaminoglycan) GAGs -- Repeating disaccharides -- cationic -- e.g., Chondroitin Functions hydroscopic swelling pressure influence cell migration Cell Communities

  7. How are cells linked together and to extracellular matrix? May involve Cytoskeleton and components Of extracellular matrix Cell Communities

  8. What creates Cell-Cell linkages? Cadherins mediate cell-cell linkage -- many types: C-, E-, P-, T- cadherins -- “homophillic” binding Can be connected to cytoskeleton Desmosomes – intermediate filaments Adherin junctions – actin filaments Classic newt embryo experiment -- Townes and Holfreter (1955) (simplified) Cadherins Cell Communities

  9. Linkage to the ECM are also important Integrins – mediate linkages between cytoskeleton and ECM Also can be connected to cytoskeleton Hemidesmosomes – intermediate filaments Contact Adhesions – actin filaments linkages are ‘responsive’ Question 20-4 Why are these linkages more common in fibroblasts, and desmosomes and adherin junctions more common in epithelial cells? Cell Communities

  10. We arise from stem cells How are stem cells different from normal cells? Types of stem cells Embryonic vs Adult Totipotent vs Pluripotent Cell Communities

  11. Adult stem cellsregenerate cells and tissues of the body Intestinal epithelium: example of a ‘simple epithelium’ Cell Communities

  12. How do somatic stem cells renew skin? Skin structure -- stratified epithelium Epidermal stem cells Example of a stratified epithelium Cell Communities

  13. Hematopoietic (blood) stem cells Produce all blood cells Located in bone marrow 150 x 109 RBC / day ( lifespan ~120 days) 5 x 1010 neutrophils / day ( ½ life ~6-8 hours) Immature cells called ‘blast cells’  ‘lymphoblastic leukemia’ Target of bone marrow transplants Cell Communities

  14. Embryonic stem cells can be used to repair tissue and organ damage Must culture and induce differentiation Creating embryonic Stem cell lines Cell Communities

  15. Technologies are being developed for alternatives to Embryonic stem cells Cell Communities

  16. Adipose stem cells appear to have great potential as an alternative to embryonic stem cells Trachae Cell Communities

  17. Unfortunately, stem cells are prone to becoming cancerous Have capacity for perpetual cell division -- telomere lengthening Key characteristic of cancer Will discuss in next chapter Cell Communities

  18. How does loss of genetic stability lead cells to become cancerous?? Benign tumor vs Malignant tumor vs Cancer Evolutionary process Lost dependence of extracellular regulation -- checkpoint failure Loss of ‘mortality’ (e.g., telomere renewal) Activation of genes for motility and invasiveness -- cell junction breakage -- cytoskeletal changes Altered metabolism -- higher glycolysis, less Krebs – why? Abnormal adhesion proteins -- cadherins, etc -- growth in new areas Cell Communities

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