Movement of Substances

Types
1. Passive
  1. Does not require energy
  2. Move ↓ conc. gradient
  3. Eg.
    1. Diffusion
    2. Osmosis
2. Active
  1. Requires energy
  2. Move against / up conc. gradient
Diffusion
1. NET movement of particles frm a region of HIGH conc. to LOW conc.
  1. Down conc. gradient
    1. Conc. gradient
      1. Diffeence in conc. btw 2 regions
      2. Steeper grad.
        ↑ rate of diffusion
2. Factors affecting RATE
  1. Conc. gradient
    1. Steeper
      1. ↑ rate
  2. Temperature
    1. ↑
      1. ↑ energy level of molecules
        ↑ rate
  3. Size of particles
    1. ↓
      1. ↓ energy required to move particles
        ↑ rate
  4. Thickness of membrane
    1. Thin
      1. ↓ distance for particles to travel
        ↑ rate
    2. May be unapplicable
      1. Diffusion does not require a membrane
3. Eg.
  1. Animal cells
    1. Partially permeable membrane
      1. Allow some substances through
    2. Eg.
      1. Lungs
        Alveolus separated frm capillaries by a thin membrane
        Diffusion
        Gas exchange across membrane
      2. Small intestines
        Epithelium of villus
        One-celled thick
        ↑ of diffusion
        Digested food molecules into bloodstream
  2. Practical Application
    1. Kidney Dialysis
      1. Diffusion
        Wastes products removed frm blood through artificial membrane in machine
        Blood cells & large molecules retained
Osmosis
1. NET movement of WATER molecules frm a region of ↑ WATER POTENTIAL to ↓ w.p
  1. Across a PARTIALLY PERMEABLE MEMBRANE
    1. Water potential
      1. Tendency for water molecules to move frm 1 place to other
      2. Eg.
        Dilute solution
        ↑ water molecules per unit vol than a concentrated soln
2. Plants
  1. Tugor pressure

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Movement of Substances

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	Created by Elise Mac about 9 years ago