1) Discuss the different types of Fatty Acids (FA’s) that we discussed in class
ID: 972075 • Letter: 1
Question
1) Discuss the different types of Fatty Acids (FA’s) that we discussed in class (i.e., saturated, MUFA and
PUFA). A) Describe a Micelle (you should know what this is!) containing only one type of FA with specific
emphasis on the physical forces that dominate between the FA’s. B) Explain the effect of adding a different
type of FA to your Micelle. How does this affect the interactions with the previous type in (A)? C) Now
explain how the different lengths and degree of saturation would affect the interactions in your Micelle.
Explanation / Answer
Ans. 1. There are three main types of fatty acids: (i). Saturated, (ii). Monounsaturated fatty acids (MUFA) and (iii). Polyunsaturated (PUFA). All fatty acids are molecules composed mostly of carbon and hydrogen atoms.
(i). Saturated fatty acids: A saturated fatty acid has the maximum possible number of hydrogen atoms attached to every carbon atom. It is therefore said to be “saturated” with hydrogen atoms. Saturated fatty acids are mostly found in foods of animal origin.
(ii). Monounsaturated fatty acids (MUFA) : Some fatty acids are missing one pair of hydrogen atoms in the middle of the molecule. This gap is called an “unsaturation” and the fatty acid is said to be “monounsaturated” because it has one gap. Monounsaturated fatty acids are mostly found in foods of plant origin and some seafoods.
(iii). Polyunsaturated (PUFA): Fatty acids that are missing more than one pair of hydrogen atoms are called “polyunsaturated fatty acids.” Polyunsaturated fatty acids are mostly found in foods of plant origin and some seafoods. Polyunsaturated fatty acids are of two kinds: (a) omega-3 and (b) omega-6.
Recently a new term has been added to the fat lexicon: trans fatty acids. A trans- fat is an unsaturated fat with a "twist" around the double bond between two carbon atoms. The "twist" of the molecule tends to make it stick in the lining of cells, where it can be attacked by free radicals that damage the rest of the lining of the cell.
(A) Micelles are lipid molecules that arrange themselves in a spherical form in aqueous solutions. Micelles usually form in soap molecules. Soap often form micelles because they contain only one hydrocarbon chain. The formation of a micelle is a response to the amphipathic nature of fatty acids, meaning that they contain both hydrophilic regions (polar head groups) as well as hydrophobic regions (the long hydrophobic chain). Micelles contain polar head groups that usually form the outside as the surface of micelles. In soaps, the non-polar, hydrophobic, long hydrocarbon chain end of the carboxylate ion attaches to non-polar dirt, grease and oil. The hydrophilic, carboxylate anion end is attracted to polar water molecules by ion-dipole interactions. Soap micelles, clusters of soap molecules in which the hydrocarbon chains are attracted to each other by Van der Waals forces (dispersion forces, London forces, weak intermolecular forces), surround the non-polar dirt particle, with the anion heads attracted to the surrounding water. When agitated, the soil particle surrounded by soap micelles breaks free and remains dispersed in the washing water because the carboxylate anions repel each other. The soil particle surrounded by soap micelles forms an emulsion in the washing water.
(B) If saturated fatty acids was added to micelles they from Glycolipids and phospholipids. Two hydrophobic chains that are too bulky to fit into the a spherical shape as micelles do. Thus, they preferred to form glycolipids and phospholipids as "lipid bilayers".
(C) Fatty acids don’t readily form micelles until a certain concentration of fatty acids is present in a solution. Once the number of fatty acids reaches a concentration known as the critical micelle concentration (CMC), they will begin forming micelles. Above the CMC, adding more fatty acids will result in the formation of more micelles. Below the CMC, fatty acids prefer to form a layer at the surface of the water in which the water-fearing tails point up into the air and the water-loving heads stand on the water.
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