Unsaturated fatty acids have one or more double bonds. Unsaturated fats help to lower blood cholesterol levels whereas, saturated fats might contribute to plaque formation in the arteries.įigure 3.16 Saturated fatty acids have hydrocarbon chains connected by single bonds only. Olive oil, corn oil, canola oil, and cod liver oil are examples of unsaturated fats. The cis double bond causes a bend or a “kink” that prevents the fatty acids from packing tightly, keeping them liquid at room temperature ( Figure 3.16). If the hydrogen atoms are on two different planes, it is a trans fat. If hydrogens are present in the same plane, it is a cis fat. Cis and trans indicate the configuration of the molecule around the double bond. Unsaturated fats or oils are usually of plant origin and contain cis unsaturated fatty acids. Plants store fat or oil in many seeds and use them as a source of energy during seedling development. Mammals store fats in specialized cells, or adipocytes, where fat globules occupy most of the cell’s volume. Animal fats with stearic acid and palmitic acid (common in meat) and the fat with butyric acid (common in butter) are examples of saturated fats. Long straight fatty acids with single bonds generally pack tightly and are solid at room temperature. A fat may contain similar or different fatty acids attached to glycerol. When a fatty acid has no double bonds, it is a saturated fatty acid because it is not possible to add more hydrogen to the chain's carbon atoms. If there is one double bond in the molecule, then it is a monounsaturated fat (e.g., olive oil), and if there is more than one double bond, then it is a polyunsaturated fat (e.g., canola oil). Most unsaturated fats are liquid at room temperature. Stearic acid is an example of a saturated fatty acid ( Figure 3.14).įigure 3.15 Oleic acid is a common unsaturated fatty acid. In other words, the number of hydrogen atoms attached to the carbon skeleton is maximized. Saturated fatty acids are saturated with hydrogen. ![]() In a fatty acid chain, if there are only single bonds between neighboring carbons in the hydrocarbon chain, the fatty acid is saturated. Arachidic acid is derived from Arachis hypogea, the scientific name for groundnuts or peanuts.įatty acids may be saturated or unsaturated. For example, palmitic acid, a saturated fatty acid, is derived from the palm tree. Some fatty acids have common names that specify their origin. We also call fats triacylglycerols or triglycerides because of their chemical structure. The three fatty acids in the triacylglycerol may be similar or dissimilar. Three water molecules release in the process.ĭuring this ester bond formation, three water molecules are released. Lipids include fats, oils, waxes, phospholipids, and steroids.įigure 3.13 Joining three fatty acids to a glycerol backbone in a dehydration reaction forms triacylglycerol. Lipids are also the building blocks of many hormones and are an important constituent of all cellular membranes. For example, they help keep aquatic birds and mammals dry when forming a protective layer over fur or feathers because of their water-repellent hydrophobic nature. Lipids also provide insulation from the environment for plants and animals ( Figure 3.12). Cells store energy for long-term use in the form of fats. Lipids perform many different functions in a cell. Non-polar molecules are hydrophobic (“water fearing”), or insoluble in water. This is because they are hydrocarbons that include mostly nonpolar carbon–carbon or carbon–hydrogen bonds. Lipids include a diverse group of compounds that are largely nonpolar in nature. Explain how cholesterol helps maintain the plasma membrane's fluid nature. ![]()
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