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biology final test help

Terms in this set (68)

movement of molecules from an area of higher concentration of the molecules to an area of lower concentration of molecules.
7 properties
1. Diffusion is a passive process . By passive, we mean that diffusion does not require the input of energy from some outside source. Diffusion uses only the kinetic energy possessed by all molecules.
2. Molecules move from an area of higher concentration to an area of lower concentration. A difference in the concentration of
a substance between two places is called a concentration gradient aka chemical gradient . rate depends on concentration gradient. The larger the concentration difference,the faster diffusion takes place.
3. Net movement of molecules occurs until the concentration is equal everywhere. Once molecules of a given substance have distributed themselves evenly, the system reaches equilibrium and diffusion stops. Individual molecules are still moving at equilibrium, but for each molecule that exits an area, another one enters.The dynamic equilibrium state in diffusion means that the concentration has equalized through out the system but molecules continue to
move.
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. Because diffusion results from molecular movement, the rate of diffusion increases as temperature increases.
6. Diffusion rate is inversely related to molecular size. Einstein calculated that diffusion is inversely proportional to the radius of the molecule: the larger the molecule, the slower its diffusion through a given medium.
7. Diffusion can take place in an open system or across a partition that separates two systems.

- ions do not move by diffusion move by electrochemical gradients