25 - 2) 7.2, 7.3, 36.1 (130-133, 740-742) A) Purpose of...

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2) 7.2, 7.3, 36.1 (130-133, 740-742) A) Purpose of Cell Membrane’s selective permeability -Regulates transport across cellular boundaries. -Regulates traffic of substances across cell membrane with its fluid phospholipid bilayer, and its proteins to assist the movement of other substances that cannot go across membrane. -Sends wastes out of cell, and nutrients into cell. -Keeps the cell alive be regulating concentrations inside and outside the cell of many substances so that all substances move along their concentration gradient. - Hydrophobic molecules and uncharged molecules are able to move through the lipid bilayer very easily because the inside if hydrophobic. So they are able to slip through the hydrophilic heads, and through the hydrophobic tails into the cell and vice versa. - Hydrophillic molecules and ions go through membranes much more slowly because it is harder for them to penetrate lipid bilayer. -So they have to use Transport proteins like channel proteins , which act as hydrophilic tunnels for certain ions and substances of charge and carrier proteins which changes the shape of the substance it serves to enable it to leave or go into the cell. -Transport substances will only serve certain substances. Glucose transport protein will not serve to translocate fructose. B) Passive Transport -transport through membrane which does not need work or energy to do. Diffusion and Osmosis are passive transport. Diffusion -The transport of a substance along its concentration gradient from areas of higher concentration to areas of lower concentration until cell reaches a dynamic equilibrium of the substance. -requires no work done by cell
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This note was uploaded on 10/02/2011 for the course BIO 210 taught by Professor Lee during the Spring '11 term at San Mateo Colleges.

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25 - 2) 7.2, 7.3, 36.1 (130-133, 740-742) A) Purpose of...

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