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TOPIC 1: Cell Biology - Coggle Diagram

- - - - DIFFERENTIATION: specialised tissues develop by cell differentiation in multicellular organisms: Differentiation involves the expressions of some genes and not others in a cell’s genome.
      - Types of stem cells:
        totipotent (can form any cell type + extra embryonic)
        pluripotent (can form any cell type)
        multipotent (closely related cell types
        unipotent (cant diff)
        
        DIFFERENTIATION
        
        Outline differentiation of cells in a multicellular organism. 4 marks
        
        differentiation is development in different/specific ways
        
        cells carry out specialized functions/become specialized
        
        example of a differentiated cell in a multicellular organism
        
        cells have all genes/could develop in any way
        
        some genes are switched on/expressed but not others
        
        position/hormones/cell-to-cell signals/chemicals determine how a cell develops
        
        a group of differentiated cells is a tissue
      - Stem cells are required for embryonic development as they are undifferentiated cell source from which all cell types arise.
        The potency of stem cells make them suitable for therapeutic use: to replace damaged or dead cells.
        
        Stargardt’s Disease – this disease is a hereditary degenerative condition that causes blindness in children due to defective photoreceptors in retina.
        Treatment = injection of embryonic stem cells into the back of the eyeball which can differentiate into retina cells
        
        Leukemia = bone marrow cancer producing high levels of poorly effective WBC. injecting hematopetic sten cells from bone marrow and differentiating into white blood cells.
      - Ethical issues in stem cell research: suffering of patients could be reduced: stem cells developing into tumours / rejection: death of early-stage embryos
- - - - Bulk transport = membrane is held by hydorphobic interactions between the phospholipid tails = allows for membrane fluidity.
        
        Endocytosis is the infolding of membrane/formation of vesicles to bring molecules into cell with use of energy (pinocytosis = lipids/dissolved/ phagocytosis = solid)
        
        Exocytosisis the infolding of membrane/formation of vesicles to release molecules from cell with use of energy ✔
        example: Destruction of pathogen
      - The sodium-potassium pumps move
        1) three sodium ions out of the cell and
        2) two potassium ions into the cell using one ATP molecule
        The pumps are always moving the ions against their concentration gradient via active transport
        Three sodium ions from the inside of the axon bind to the pump ATP attaches to the pump and transfers a phosphate to the pump (phosphorylation), causing it to change shape and resulting in the pump opening to the outside of the axon
        The three sodium ions are released out of the axon
        Two potassium ions from outside the axon enter and bind to their sites
        The attached phosphate is released altering the shape of the pump again
        The change in shape causes the potassium ions to be released inside the axon
        When nerve cells are stimulated, sodium ion channels open and sodium ions rush in down the electrochemical gradient, reversing the charge across the membrane
- - - - membranes exhibit a characteristic 'trilaminar’ appearance
    - - mammalian membranes reduces membrane fluidity and permeability to some solutes. it is amphoteric (-OH hydrophilic, hydrocarbon chain hydrophobic).
      - Cholesterol stops the hydrocarbon from crystalizing and behaving as a solid: maintain its fluidity by disrupting the regular packing of the hydrocarbon tails
      - cholesterol also retricts molecular motion, which reduces the fluidity of the membrane
      - reduces membrane permeability to solutes to control the fludity of the memrbrane