bio2 - systems Diffusion across a membrane 8 The rate of...

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Rules for Simple Diffusion 1. Diffusion is a passive process that does not require an outside energy source. It uses only the kinetic energy of molecular movement. 2. Molecules diffuse from an area of higher concentration to an area of lower concentration. The larger the concentration difference, the faster diffusion takes place. 3. There will be net movement of molecules until the concentration is equal. Molecular movement continues, however, so this is called a dynamic equilibrium. 4. Diffusion is rapid over short distances but much slower over long distances. 5. Diffusion is directly related to temperature. At higher temperatures, molecules move faster and diffusion is more rapid. 6. Diffusion is inversely related to molecular size. The larger a molecule is, the slower it will diffuse. 7. Diffusion can take place in an open system or across a partition that separates two
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Unformatted text preview: systems. Diffusion across a membrane 8. The rate of diffusion through a cell membrane depends on the ability of the molecule to dissolve in the lipid layer of the membrane. Only lipid-soluble (lipophilic) molecules can diffuse across the membrane by simple diffusion. 9. The rate of diffusion through a membrane is directly proportional to the surface area of the membrane. The larger the surface area, the more molecules can diffuse across per unit time. 10. The rate of diffusion across a membrane is inversely proportional to the thickness of the membrane. The thicker the membrane, the slower diffusion will take place. (Reference: Table 5-2, Human Physiology, 3 rd Ed ., by Dr. Dee Silverthorn)...
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