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artificial lipid bilayer

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PERMEABILITY OF THE LIPID BILAYER. High permeability. O 2. HYDROPHOBIC MOLECULES. N 2. H 2 O CO 2 Urea Glycerol. SMALL UNCHARGED POLAR MOLECULES. LARGE UNCHARGED POLAR MOLECULES. Glucose Sucrose. artificial lipid bilayer. Na + K + Cl - Ca 2+ Mg 2+ HCO 3-. IONS.

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artificial lipid bilayer

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  1. PERMEABILITY OF THE LIPID BILAYER High permeability O2 HYDROPHOBIC MOLECULES N2 H2O CO2 Urea Glycerol SMALL UNCHARGED POLAR MOLECULES LARGE UNCHARGED POLAR MOLECULES Glucose Sucrose artificial lipid bilayer Na+ K+ Cl- Ca2+ Mg2+ HCO3- IONS Low permeability Specific membrane proteins are responsible for transferring large uncharged polar molecules and ions across cell membranes

  2. Transport across the plasma membrane • Diffusion (passive) • Osmosis (passive) • Active transport (active) • Endocytosis (in..e.g.phagocytosis) and Exocytosis (out..e.g.secretion –lysosomes fusing with membrane and releasing contents to the outside of the cell)

  3. Diffusion • The net movement of molecules or ions from a region where they are more highly concentrated to one where their concentration is lower.

  4. Dynamic equilibrium: the particles are still changing position but the concentration remains evenly distributed.

  5. Rate of diffusion • Concentration gradient • Area over which diffusion takes place • Thickness of exchange surface Surface area x difference in concentration/ length of diffusion path

  6. Facilitated diffusion (1) • Protein channels • They are water filled so glucose and amino acids (water soluble) can diffuse through. • Channels only open in the presence of specific molecules so that there is control over the entry and exit of substances

  7. Facilitated diffusion (2) • Carrier proteins • When a particular molecule that is specific to the protein is present, it binds with the protein. This causes it to change shape in such a way that the molecule is released to the inside of the membrane.

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