BY1.3 - Transport Across the Membrane

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Transport Across the Membrane 

The membrane is selectively permeable to water and some solutes

Lipid soluble subatnces move mroe easi;ly tahn wtaer soluble ones

Small uncharged molecules (e.g. oxygen, cabron dioxide) can pass freely through

Lipid soluble moelcuels (e.g. glycerol) pass through 

The hydrophobic core stops the transport of ions and polar molecules 

The intrinsic proteins assist the particles i and out by a passive provess called facilitated diffusion


  • The movmement of ions/molecules rom an area of high concnetration to an area of low concnetration until equilibrium is reached 
  • Affected by:
    • Concentration gradient: 
      • The greater the difference in concentrations, the greater the rate
    • Distance:
      • The shorter the distance, the greater the rate 
    • Surface Area:
      • The larger the surface area, the gretaer the rate
    • Thickness:
      • The thinner the surface, the greater the rate
    • Temperature:
      • An increase in temperature, leads to an increase in molecular kinetic energy and so more…


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