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Unformatted text preview: Name: , DL Section: Last First Office Use Quiz 4 Physics 7B Winter 2010 Feb. 03, 2010 In many cases, cell growth is limited by the ability to diffuse oxygen into the cell and carbon-dioxide out. Consider a single-celled organism (amoeba); assume that it is spherical in shape. The amount of cellular respiration is proportional to the volume of the cell. Consider the CO 2 concentration to be uniform both outside and inside the cell; the diffusion gradient exists only across the lipid bi-layer cell wall. The diffusion constant for CO 2 across a cell wall is 0.35 cm 2 /s; the cell wall is 50 nm (1 nm = 10-9 m) thick. a) Assume that the CO 2 concentration inside the cell is three times higher than it is in the surrounding environment when the amoeba has reached a size of 50 m (1 m = 10-6 m) in radius. CO 2 levels which are five times higher than the surrounding environment are toxic to the amoeba. How large can this amoeba grow before it must divide or die? Show your work. Lets think about this a little Respiration produces CO 2 , therefore the rate of CO 2 production is proportional to the volume of the cell (i.e. proportional to production is proportional to the volume of the cell (i....
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- Winter '10