|MadSci Network: Cell Biology|
Hi Jennie, So I see that you are most likely extracting pigments from beet root and using ethanol to disrupt membranes? If not, its a fun experiment. Ethanol disrupts membranes by a number of methods. In particular what you must remember is, the size and fluidity of the membrane has a lot to do with the outside and inside environment. This environment consists of how much water, salts etc are in the cell versus out of the cell. Adding ethanol disrupts much of this. 1. Ethanol is permeable to cell membranes. Because of the nature of ethanol as a chemical is it able to get into the cell very easily. This disrupts the balance of the cells' osmotic environment. Osmosis is the movement of water. Think about what happens if you fill a balloon too full. What happens? It expands and stretches the membrane of the balloon. If you release too much water from the balloon it crumples the membrane and deflates, no longer keeping it structure. This is the same in a cell. Ethanol disrupts this flow. It has also been shown that ethanol can disrupt the ion channels in the plasma membrane. These channels in the cell membrane help pump ions like calcium and potassium in and out of the cell which directly control how much water is pumped in and out of the cell (remember the balloon). 2. Ethanol disrupts water. What I mean by this is that ethanol has the ability to make hygrogen bonds. These are the weak, yet plentiful, bonds a hydrogen atom can make with a negative atom like oxygen or nitrogen. If you don't remember hygrogen bonds, please look them up. They are not ionic bonds nor covalent bonds, but rather weak attractive forces between hydrogen and a semi-negative charged oxygen or nitrogen. Hydrogen bonds are one of the major reasons we have life on earth. Hydrogen bonds give water its properties including how water molecules organize themselves. Ethanol get inbetween these water molecules and disrupts their organization. And yes, liquid water is an organized fluid. Not quite as organized as frozen water (ice) but organized none the less. When ethanol disrupts this organization, it too can also disrupt how the hydrophilic (water loving) regions of the plasma membrane interacts with the water. Disrupting these interactions can change the structure of the membranes. Put that together with an environment where ethanol is also messing up the proper flow of ions and water and you have an instable environment. This is enough to break the membranes open and in many cases, dehydrate the cells. If you are extracting pigments, ethanol is also the perfect solute for pigments and therefore helps in the extraction process. I hope this helps! Matt
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