Introduction to Cells

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  • Created by: sofiedb
  • Created on: 20-11-17 17:57
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  • Introduction to cells (smallest unit of life)
    • Cell theory
      • living organisms are composed of 1+ cells
      • cells are the basic units of structure & organisation in organisms
      • cells come from pre-existing cells
    • Microscope
      • light microscope: all plant & animal tissues are made up of individual cells (structure)
      • electron microscope (higher resolution): full complexities of internal fine structure of cells  - ultrastructure
    • "the evolution of multicellular organisms allowed cell specialization and cell replacement."
      • advantage of multicellular: severe damage to cell does not mean end of organism
        • Virus: non-living (protein coat & DNA/RNA // no metabolism & reproduction & no cellular structure (functions may be carried out by infected host cell)
    • Organisms
      • Unicellular organisms (bacteria, archaea, protozoa, unicellular algae)
        • A single, living cell can carry out all life functions
      • Multicellular organisms
        • Increase in organism's size --> cell differentiation --> emergent properties
        • Stem cells --> specialisation (self-replicate/ differentiation
          • synthesis of certain proteins triggers specialised development of a specific cell & its descendants
          • totipotent: any type, rise to complete organism
          • pluripotent: all body cells, no rise to complete organism
          • multipotent: several closely related types
          • unipotent: associated cell type
          • embryo: important source of stem cells
            • 1. removal of nucleus from donor egg cell
              • 2. nuclear transfer of host DNA from somatic cells
                • 3. 4-cell-stage
                  • 4. blastocyst
                    • 5. embryo stem culture containing DNA from adult host
          • Stargardt's disease (retinal cells)/leukaemia (haematopoetic stem cells)
          • sources
            • specially created embryos
            • umbilical cord blood
              • low risk of tumour formation/ less concern/less accumulated mutations
                • limited cells
            • adult's own tissue
              • low risk of tumour formation/no issue with consent
                • limited cell types/high chance of genetic damage (mutations during lifetime)
    • Life functions (MR H. GREN)
      • Metabolism: regular set of life-supporting reactions that take place within the cells
      • Response: reaction to changes in the environment
      • Homeostasis: the maintenance of a constant internal environment by regulating internal cell conditions
      • Growth: a positive change in size/shape over time
      • Reproduction: production of offspring to pass on genetic information to the next generation
      • Excretion: removal of waste products of metabolism and other unimportant materials
    • SA:V
      • import of molecules & expulsion of waste products through plasma membrane
        • SA to small:V too large - not enough import/excretion (division)

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