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You are watching: What prevents lipids from mixing with water

Lipids Fats, oils, and also waxes space all instances of lipids. Over there are many lipids, but they every share the trait of gift at least partially hydrophobic (meaning castle won"t mix v water). Water molecules space polar due to the fact that they have actually positive and an adverse ends, rather like tiny magnets. Many lipids are non-polar (having no fee areas) or only slightly polar, through a very few charged areas. Water mixes v hydrophilic (water-loving) link by sticking to their charged groups. Due to the fact that lipids absence charged groups, the water molecules have nothing to stick to and don"t mix through them. (Think of do the efforts to choose up a glass marble through a magnet). Lipids deserve to be inserted in three significant groups: triglycerides (fats & oils), phospholipids (making up cabinet membranes), and steroids (many hormones).

Testing the Polarity the Lipids We can use chromatography to separate out mixtures of chemicals and tell us something about their properties. Drops of unknowns space blotted near the bottom that a color layer analyzer strip. The basic of the strip is collection in a solvent, and the solvent soaks its way up the strip prefer water move up a sponge. The solvent additionally takes some of the unknowns together with it. Chemicals v a polarity similar to the solvent will certainly be dissolved by it and also move along the solvent front. Little molecules will relocate along quicker than large ones. By looking in ~ how much various chemicals move along the strip, friend can obtain a feeling for how polar lock are and also sometimes additionally how large they are. In this case, we placed three unknowns on a color layer analyzer strip: a phospholipid, a triglyceride, and also a fatty acid. Our score is to sort out i m sorry is which based on their properties. Our solvent is non-polar, and also so have to mix well with other non-polar substances and carry them along with it. We recognize that the an ext polar a compound, the tighter it need to stick come the silica the the chromatography strip. Phospholipids shouldn"t move at all from wherein they are put on the strip, whereas triglycerides room non-polar and shouldn"t stick at every to the strip. Fat acids should fall somewhere in between.

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Rf Values

Rf A = 2.4 cm/ 6.5 cm = 0.4 Rf B = 0 cm/ 6.5 cm= 0.0Rf C =4.3 cm/ 6.5 cm= 0.7 Note: dimensions are taken from the facility of the darkest blotch in every lane.


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Calculations: Rf worths

Rf values are a numerical way of to compare the motion of various substances along a chromatography strip. The Rf is same to the full distance a substance travel (measure native the center of the blotch) separated by the complete distance the solvent prior moved. A substance the didn"t move at all would have an Rf of zero, while a substance that relocated right v the solvent prior would have actually an Rf that one. ranges can be calculated native the photo over by individually the final point to i beg your pardon something traveled from the point at which the started. Because that example, samples to be blotted on at the 8.3 centimeter mark and the solvent quit at the 1.8 cm mark. The solvent for this reason traveled 6.5 cm (or 8.3 cm - 1.8 cm).

Class chromatography Results based upon class results, C moved fastest, A next fastest, and B didn"t move (though you can see some smudging in every lanes native impurities). Thus, C should be non-polar like our solvent, A slightly polar, and B so polar that it couldn"t be relocated off the silica. Triglycerides are non-polar, and also should dissolve automatically in our non-polar solvent. Thus, C seems choose a good candidate for our triglyceride sample. Phospholipids should adhere come the silica, which seems to match up with lane B. Fatty acids are slightly polar, i beg your pardon is the best match for roadway A. can you see how the quantity of polarity a substance has correlates through how rapid it moves up the color layer analyzer strip?