Fat and Why it Matters
Overview of lipids, covering fats and oils, saturated and unsaturated fats, triglycerides (triacylglycerols), phospholipids, and steroids. A fat molecule consists of two kinds of parts: a glycerol backbone and three fatty acid tails. To make a fat molecule, the hydroxyl groups on. Definitions of Fat Components Fats and Oils: Saturated vs Unsaturated Fats trans Fats This gives us a better image, in terms of the size relationship of the glycerol group on The hydrocarbon tails of unsaturated phosophlipids are kinked. Nutrition - Lipids (fats and oils): Another form in which some plants store energy Similar relationships occur among organic nutrients and originate for several.
- Fats and oils
- 17.2: Fats and Oils
- The Kinds of Fats
So, fats with unsaturated tails tend to be liquid at room temperature have a relatively low melting point — they are what we commonly call oils. For instance, olive oil is mostly made up of unsaturated fats 2 2. Trans fats are rare in nature, but are readily produced in an industrial procedure called partial hydrogenation. In this process, hydrogen gas is passed through oils made mostly of cis-unsaturated fatsconverting some — but not all — of the double bonds to single bonds.
Trans-unsaturated fatty acids can pack more tightly and are more likely to be solid at room temperature. Partial hydrogenation and trans fats might seem like a good way to get a butter-like substance at oil-like prices.
Unfortunately, trans fats have turned out to have very negative effects on human health. Because of a strong link between trans fats and coronary heart disease, the U. Food and Drug Administration FDA recently issued a ban on trans fats in foods, with a three-year deadline for companies to remove trans fats from their products 4 4. Omega fatty acids Another class of fatty acids that deserves mention includes the omega-3 and omega-6 fatty acids. There are different types of omega-3 and omega-6 fatty acids, but all of them are made from two basic precursor forms: Some fish, such as salmon, and some seeds, such as chia and flax, are good sources of omega-3 fatty acids.
Omega-3 and omega-6 fatty acids have at least two cis-unsaturated bonds, which gives them a curved shape. Omega-6 fatty acids are defined analogously, with the first double bond located between the sixth and seventh carbons from the omega end. Image of alpha-linoleic acid ALAshowing its curled shape due to its three cis double bonds. Omega-3 and omega-6 fatty acids play a number of different roles in the body.
They are precursors starting material for the synthesis of a number of important signaling molecules, including ones that regulate inflammation and mood. Omega-3 fatty acids in particular may reduce the risk of sudden death from heart attacks, decrease triglycerides in the blood, lower blood pressure, and prevent the formation of blood clots. However, fats are essential to the body and have a number of important functions. For instance, many vitamins are fat-soluble, meaning that they must be associated with fat molecules in order to be effectively absorbed by the body.
Fats also provide an efficient way to store energy over long time periods, since they contain over twice as much energy per gram as carbohydrates, and they additionally provide insulation for the body.
Like all the other large biological molecules, fats in the right amounts are necessary to keep your body and the bodies of other organisms functioning correctly. Waxes Waxes are another biologically important category of lipids. Wax covers the feathers of some aquatic birds and the leaf surfaces of some plants, where its hydrophobic water-repelling properties prevent water from sticking to, or soaking into, the surface.
Image of shiny leaf surface covered with wax. Structurally speaking, waxes typically contain long fatty acid chains connected to alcohols by ester linkages, although waxes produced by plants often have plain hydrocarbons mixed in as well 6 6. Phospholipids What keeps the watery goo cytosol inside of your cells from spilling out?
Cells are surrounded by a structure called the plasma membrane, which serves as a barrier between the inside of the cell and its surroundings. Specialized lipids called phospholipids are major components of the plasma membrane. Like fats, they are typically composed of fatty acid chains attached to a backbone of glycerol. Instead having three fatty acid tails, however, phospholipids generally have just two, and the third carbon of the glycerol backbone is occupied by a modified phosphate group.
Different phospholipids have different modifiers on the phosphate group, with choline a nitrogen-containing compound and serine an amino acid being common examples. Different modifiers give phospholipids different properties and roles in a cell. Structure of a phospholipid, showing hydrophobic fatty acid tails and hydrophilic head including ester linkages, glycerol backbone, phosphate group, and attached R group on phosphate group.Fats/Lipids Lecture
A bilayered membrane consisting of phospholipids arranged in two layers, with their heads pointing out and their tails sandwiched in the middle, is also shown. A phospholipid is an amphipathic molecule, meaning it has a hydrophobic part and a hydrophilic part. The hydrocarbon tails dissolve in the soil; the ionic heads remain in the aqueous phase, and the soap breaks the oil into tiny soap-enclosed droplets called micelles, which disperse throughout the solution.
The droplets repel each other because of their charged surfaces and do not coalesce. The double bonds in fats and oils can undergo hydrogenation and also oxidation. The hydrogenation of vegetable oils to produce semisolid fats is an important process in the food industry. Chemically, it is essentially identical to the catalytic hydrogenation reaction described for alkenes.
In commercial processes, the number of double bonds that are hydrogenated is carefully controlled to produce fats with the desired consistency soft and pliable. Inexpensive and abundant vegetable oils canola, corn, soybean are thus transformed into margarine and cooking fats. In the preparation of margarine, for example, partially hydrogenated oils are mixed with water, salt, and nonfat dry milk, along with flavoring agents, coloring agents, and vitamins A and D, which are added to approximate the look, taste, and nutrition of butter.
Preservatives and antioxidants are also added. In most commercial peanut butter, the peanut oil has been partially hydrogenated to prevent it from separating out.
Consumers could decrease the amount of saturated fat in their diet by using the original unprocessed oils on their foods, but most people would rather spread margarine on their toast than pour oil on it. Many people have switched from butter to margarine or vegetable shortening because of concerns that saturated animal fats can raise blood cholesterol levels and result in clogged arteries. However, during the hydrogenation of vegetable oils, an isomerization reaction occurs that produces the trans fatty acids mentioned in the opening essay.
However, studies have shown that trans fatty acids also raise cholesterol levels and increase the incidence of heart disease. Trans fatty acids do not have the bend in their structures, which occurs in cis fatty acids and thus pack closely together in the same way that the saturated fatty acids do.
Fats and oils that are in contact with moist air at room temperature eventually undergo oxidation and hydrolysis reactions that cause them to turn rancid, acquiring a characteristic disagreeable odor. One cause of the odor is the release of volatile fatty acids by hydrolysis of the ester bonds. Butter, for example, releases foul-smelling butyric, caprylic, and capric acids.
Microorganisms present in the air furnish lipases that catalyze this process.
All About Lipids – Fats and Oils
Hydrolytic rancidity can easily be prevented by covering the fat or oil and keeping it in a refrigerator. Another cause of volatile, odorous compounds is the oxidation of the unsaturated fatty acid components, particularly the readily oxidized structural unit in polyunsaturated fatty acids, such as linoleic and linolenic acids. One particularly offensive product, formed by the oxidative cleavage of both double bonds in this unit, is a compound called malonaldehyde. Rancidity is a major concern of the food industry, which is why food chemists are always seeking new and better antioxidants, substances added in very small amounts 0.
Antioxidants are compounds whose affinity for oxygen is greater than that of the lipids in the food; thus they function by preferentially depleting the supply of oxygen absorbed into the product.
Fats and oils - Better Health Channel
Because vitamin E has antioxidant properties, it helps reduce damage to lipids in the body, particularly to unsaturated fatty acids found in cell membrane lipids. Summary Fats and oils are composed of molecules known as triglycerides, which are esters composed of three fatty acid units linked to glycerol. The hydrolysis of fats and oils in the presence of a base makes soap and is known as saponification. Double bonds present in unsaturated triglycerides can be hydrogenated to convert oils liquid into margarine solid.
The oxidation of fatty acids can form compounds with disagreeable odors. This oxidation can be minimized by the addition of antioxidants. Concept Review Exercises What functions does fat serve in the body? Which of these triglycerides would you expect to find in higher amounts in oils? Answers Fats provide energy for living organisms. They also provide insulation for body organs and transport fat-soluble vitamins. The triglyceride on the left is expected to be present in higher amounts in fats because it is composed of a greater number of saturated fatty acids.