What Elements Are Found in Lipids? | Sciencing
Fatty Acids Soaps and Detergents Fats and Oils Waxes Phospholipids Eicosonoids Terpenes Steroids Lipid Soluble Vitamins Biosynthetic Pathways. danunah.info Chemistry of Oils and Fats. What Are Oils and Fats? Like most organic materials, Oils and fats are made up of three elements: • Carbon. Oil is a type of lipid known as a triglyceride. Solid triglycerides are known as fats and liquid triglycerides are called oils. Credit: Thomas Vogel/E+/Getty Images.
Because these substances are not miscible in water, washing with water alone does little to remove them. Soap removes them, however, because soap molecules have a dual nature.
One end, called the head, carries an ionic charge a carboxylate anion and therefore dissolves in water; the other end, the tail, has a hydrocarbon structure and dissolves in oils. 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.
17.2: Fats and Oils
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.
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.
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?
Fats and Other Lipids - Diet and Health - NCBI Bookshelf
Which of these triglycerides would you expect to find in higher amounts in oils? The physical properties of fats depend on the fatty acids that they contain. All fats are liquid when present in living tissues.
The fats of warm-blooded animals can, of course, have a higher freezing point than that of cold-blooded animals such as fish. Plants that survive frosts must have a particularly low freezing point.
Fatty acids differ from one another in two ways: Chain length varies from 4 to 22 carbons, with most fatty acids having 16 or 18 carbons.
However, a greater effect of liquidity comes from the introduction of unsaturated double bonds in the chains. More than one double bond polyunsaturation makes it more difficult for fats to remain solid at room temperature.
Animals generally either store absorbed fatty acids or oxidize them immediately as a source of energy. Particular fatty acids are needed for the production of phospholipidswhich form an essential portion of cell membranes and nerve fibres, and for the synthesis of certain hormones.
Animals can synthesize their own fat from an excess of absorbed sugars, but they are limited in their ability to synthesize essential polyunsaturated fatty acids such as linoleic acid and linolenic acid. Thus, fatty acids are not just an alternative energy source—they are a vital dietary ingredient. The main vegetable oils are good sources of linoleic acid, and most of these also contain a smaller proportion of linolenic acid.
Cats have lost one of the principal enzymes used by other animals to convert linoleic acid to arachidonic acid, which is needed for the synthesis of prostaglandins and other hormones.
Since arachidonic acid is not found in plants, cats are obligate carnivoresmeaning that under natural conditions they must eat animal tissue in order to survive and reproduce. Proteins The main organic material in the working tissue of both plants and animals is proteinlarge molecules containing chains of condensed units of some 20 different amino acids.
In animals, protein food is digested to free amino acids before entering the bloodstream. Plants can synthesize their own amino acids, which are required for protein production, provided they have a source of nitrate or other simple nitrogenous compounds and sulfurneeded for the synthesis of cysteine and methionine. Animals can also synthesize some amino acids from ammonium ions and carbohydrate metabolites; however, others cannot be synthesized and are therefore dietary essentials.
Two amino acids, cysteine and tyrosinecan be synthesized only by metabolism of the essential amino acids methionine and phenylalaninerespectively.
Bacteria living in the rumen of ruminant animals can synthesize all the amino acids commonly present in protein, and the true stomach of the ruminant will continue to receive microbial protein of reasonably good quality for digestion. Animals need protein to grow.
This requirement is roughly proportional to the growth rate and is reflected in the protein content of the milk secreted during the suckling period.
In contrast, humans take approximately days to double their birth weight, and breast milk contains protein at a level equivalent to only about 8 percent of the total energy. Young animals fed experimental diets completely lacking one essential amino acid all exhibit an immediate cessation of growth. Adults, too, require protein in fairly large amounts, more than would be needed to replace the small amount of protein lost by the body through urinefecesand shed hair and skin.
Normally, this is not a disadvantage, since the diets of adult animals, including humans, contain more protein than is required to balance the idling losses.
It also appears that, in the course of evolutionthe idling rates have become roughly adjusted to the normal protein intake. Thus, adult rodents living on a range of foods—some quite low in protein—need no more than 5 percent of their energy in the form of protein. In contrast, cats, whose ancestral carnivorous diet was much higher in protein, need some 20 percent in their diet to balance minimal losses. Vitamins Vitamins may be defined as organic substances that play a required catalytic role within the cell usually as components of coenzymes or other groups associated with enzymes and must be obtained in small amounts through the diet.
Vitamin requirements are specific for each organism, and their deficiency may cause disease. Vitamin deficiencies in young animals usually result in growth failure, various symptoms whose nature depends on the vitamin, and eventual death. Although a vitamin is usually defined as an organic chemical which an animal or human must obtain from the diet in very small amounts, this is not entirely true.
Vitamin A does not occur in the plant kingdom, but the pigment carotene is universally present in green plants, and most animals can split a molecule of carotene into two molecules of vitamin A.
The exceptions are cats and probably other carnivores, which under natural conditions have to obtain the preformed vitamin by consuming the tissues of other animals. Niacintoo, is not an absolute requirement, since most animals cats again being an exception can synthesize it from the amino acid tryptophan if the latter is present in excess of its use for protein synthesis. Vitamin D is not a true vitamin: The vitamin is subsequently metabolized to form a hormone that acts to control the absorption and utilization of calcium and phosphate.
Animals such as rodentswhich normally have little exposure to sunlight and search for food mostly at night, appear to have evolved so as to be independent of vitamin D so long as their intakes of calcium and phosphate are well-balanced. Vitamin C ascorbic acid is an essential chemical in the tissues of all species, but most can make it for themselves, so that for them it is not a vitamin. Presumably, species that cannot synthesize vitamin C—they include humans, guinea pigs, and fruit-eating bats—had ancestors that lost the ability at a time when their diet was rich in ascorbic acid.
Bacteria vary greatly in their need for vitamins. Many are entirely independent of outside sources, but at the other extreme some of the strains of bacteria found in milk i. This property has made them useful for assaying extracts of foods for their vitamin B content. Indeed, many vitamins of this group were first discovered as growth factors for bacteria before being tested with animals and humans.