Cell biology- HF

  • Created by: hkf13
  • Created on: 16-06-18 17:44
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  • Cell Biology
    • SA:V ratio
      • A way of describing how close every internal part is to the surface
      • Surface area/ volume
      • A low ratio means parts of the objects are  large way from edge
        • Heat energy takes longer to enter or escape
      • A high SA:V ratio means parts of the objects are a short distance from the edge
        • Heat energy takes short times to enter or escape
    • Diffusion
      • The movement of molecules from an area of High Conc, to an area of Low Conc
      • Diffusion either happens to substances in liquids or in gases
      • The steeper the concentration, the more likely the particles are to diffuse down the conc.
      • The larger the surface area, the more particles can diffuse at once
      • Temperature can affect rate of diffusion- the more kinetic energy, the particles spread out quicker
    • Cells
      • Take in glucose and oxygen
      • Remove waste products that are needed somewhere else in body. EG. CO2
      • Movement of materials in and out of cell via cell membrane can be by diffusion
      • Small Organisms
        • Diffusion across body surface is sufficient- less than 0.5mm
        • Large SA
        • Body or cell surface acts as exchange surface
      • Surface exchange
        • Needs- SA:V ratio is insufficient Exchange distances are too great
        • To overcome this- Specialised exchange surface and efficient transport system
    • Adaptations
      • Animals- Small intestines Mammal lungs Fish Gills
      • Plants- roots and leaves
    • Diffusion in humans
      • Lungs- oxygen for respiration
        • Adaptations- Large SA thin linings of aveoli and capillaries moist membranes
      • Gut- amino acids and starch break down protein
    • Osmosis
      • Movement of water from an area of high conc. to an area of low conc. through a partially permeable membrane
      • we need a balance of solutes for a cell to work properly
      • Isotonic- when the conc of solutes in solution are same as internal conc
      • Hypertonic- when conc of solutes outside is higher than conc inside cell
        • If the cell becomes too concentrated, cell will shrivel and die
      • Hypotonic- when conc is higher inside cell than outside
        • If cell becomes too dilute, it will shrivel and die
      • Plants need fluid around cell to be hypotonic.        Cells are turgid.


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