How A Membrane Affect An Element Rate Of Diffusion And Which Elements Can Not Penetrate Through The Membrane

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The purpose of this lab is to demonstrate how the composition of a membrane will affect an elements rate of diffusion and which elements can or cannot penetrate through the membrane.


First, it is hypothesized that methylene blue will not travel as far as potassium permanganate in the gel solution because the particle size and rate of diffusion is inversely related. Second, it is also hypothesized that the water tube placed into the beaker filled with sucrose will decrease in volume and the sucrose tube placed into the beaker filled with water will increase in volume because a cell placed into a hypertonic solution will shrink and a cell placed in a hypotonic solution will swell. Third, it is hypothesized that the starch filled tube will experience a color change, whereas the water and iodine solution will remain the same color because starch is not permeable to the membrane and iodine can freely pass through the membrane.


A cell membrane functions as a selective barrier between the cytoplasm and the extracellular fluid. This allows the cell to monitor what is permitted into and out of the cell because some molecules are permeable and others are not. The membrane is composed of phospholipid molecules that are characterized by their amphipathic nature, which means there is a polar and nonpolar end of the molecule. The head is water loving or hydrophilic and the tail is lipid loving or lipophilic. The difference in
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