Total Carbohydrates, Uses and Function of Carbohydrate - Essay Example

Carbohydrate Introduction Nature seems to have made it difficult for the chemist to carry out his work of preparing and separating substances which can find a place in his scientific system. On the other hand, the naturally separated units of organisms and their organs are often characterized by special substances so that the chemist's work can easily be based on these biological units. To this extent the chemical investigation of organisms or foods was facilitated. The importance of such chemical work for medicine and for the understanding of organismic functions was often recognized but it was a long way from a chemical analysis to an explanation of life processes. The apparent simplicity of these processes proved deceptive. The number of chemically definable units increased with accelerated speed from the beginning of the nineteenth century. Toward its end, the very multiplicity which sometimes became confusing made it possible to solve many problems. The genius of the great "natural philosophers" of earlier times had its successors in the genius of chemists who constructed a new unity by fitting together separate pieces of special experience. At first, however, the organismic products had to be taken apart and transferred from a biological system to that of elements and molecules. In 1827 William Prout (1785- 1850) distinguished between three groups of food materials: fats, proteins, and sugars. From the combustion of sugars which he carried out he concluded that sugars are related to starch and characterized by containing oxygen and hydrogen in the proportions in which these elements are present in water. They are hydrates of carbon, or carbohydrates. The conversion of starch into the sugar found in grape juice (glucose) was carried out by Gottlieb Sigismund Kirchhoff, a German pharmacist in Russia, in two ways: by heating with dilute sulfuric acid or by digesting with the "gluten" of malt (1811, 1814). Glucose was also obtained by the action of certain specific plant extracts on substances like amygdaline or salicin. Latirent proposed to call these substances "glucosamides" (1852) which Gerhardt simplified to "glycosides." They are split by enzymes into glucose and such complex materials as the nitrile of benzaldehyde (Foster-Powell, K., Brand Miller, 1995). When Alexander Butlerow (1828- 1886, Kasan) subjected a new substance, which was later found to be formaldehyde, to a digestion with limewater, he obtained (1861) "the first example of the synthetic production of a substance which behaves like a sugar." Baeyer explained this reaction (1870) as starting from a hydrate of formaldehyde, CH 2 ((OH) 2, and consisting of a combination of six such molecules with removal of six molecules of water. The sugar thus had the formula COH(C [OH] H) 4.CH 2 0H. This speculation used the results of an investigation of mannit, an alcohol obtained from manna. Berthelot, as a sequence of his work on the tribasic alcohol glycerine, recognized mannit as a hexabasic alcohol 1860); its reduction to the hydrocarbon hexane, by means of hydroiodic acid, proved the arrangement of the carbon atoms in a straight chain. This proof, in turn, was possible only because of the comparison of this hexane with other hydrocarbons. A. Wurtz applied his findings of aldehyde condensations, in which only two aldehyde molecules were involved, to the problem of the constitution of glucose. Oxidations to sugar acids and reduction to mannit were further helps in solving the problem. The chemical constitution of fructose, which is combined with glucose in cane sugar (sucrose), could be interpreted (1880) from the acids obtained by oxidizing the addition compound with hydrocyanic acid (Foster-Powell, Miller, 1995). Cellulose also belongs to the group of carbohydrates, since the addition of molecular water, under the influence of strong sulfuric acid, converts it into glucose (Braconnot, 1819). Wood contains a large proportion of cellulose and lignin. The two call be separated, according to Anselme Payen ( 1795- 1871, Paris), since nitric acid dissolves the lignin and leaves the cellulose, while sulfuric acid dissolves the cellulose and leaves the lignin as a solid residue (Foster-Powell, K., Brand Miller, 1995). The chemical constitution of the sugars was thus brought into relationship to the constitution of aldehydes and alcohols. This connection between sugars and alcohols had nothing to do with the conversion of sugar into alcohol by fermentation. The reactions used for finding the arrangement of the atoms in the molecule of sugar seemed to be much more complicated than the direct interpretation of the cleavage by fermentation. Later developments, however, showed how complicated the fermentation reaction really is. Total Carbohydrates Carbohydrate, any of a large group of compounds in which hydrogen and oxygen, in the proportions in which they exist in water, are combined with carbon; the formula of most of these compounds may be expressed as Cm(H2O)n. Structurally, however, these compounds are not hydrates of carbon, as the formula would seem to indicate. Carbohydrates, as a class, are the most abundant organic compounds found in nature. They are produced by green plants and by bacteria using the process known as photosynthesis, in which carbon dioxide is taken from the air by means of solar energy to yield the carbohydrates as well as all the other chemicals needed by the organisms to survive and grow (www.encarta.msn.com%A0/encyclopedia_ 761577934/Carbohydrate.html). Within living organisms, carbohydrates serve both essential structural and energy-storage functions. In plants, cellulose and hemicellulose are the main structural elements. In invertebrate animals, the polysaccharide chitin is the main component of the exoskeletons of arthropods. In vertebrate animals, the cell coatings of connective tissues contain carbohydrates. Cell membranes are rich in glycoproteins. Plants use starch and animals use glycogen to store energy; when the energy is needed, the carbohydrates are broken down by enzymes (www.encarta.msn.com%A0/encyclopedia_ 761577934/Carbohydrate.html). Carbohydrates provide energy for the brain, central nervous system, and muscle cells. They are found largely in sugars, fruits, vegetables, and cereals and grains. Meats generally have no carbohydrates. There are simple carbohydrates, such as sugars, and complex carbohydrates, such as breads and pastas, which the body breaks down into sugars. Someone with a 2,000-calorie-per-day diet should limit carbohydrates to 300 grams. Someone with a 2,500-calorie-per-day diet can consume up to 375 grams of carbohydrates. A medium baked potato with skin has 51 grams of carbohydrates, an apple has about 21 grams, a tablespoon of sugar has 12 grams, and a slice of pie can contain 60 or more grams of carbohydrates. Carbohydrates are divided into three kinds: monosaccharide or simple sugars, such as glucose and fructose; disaccharides-composed of two monosaccharide-such as maltose, sucrose, and lactose; and polysaccharides, which are starches and glycogen. On the nutrition facts label, total carbohydrates are broken down into two categories: fiber and sugar. Sugars in foods are the monosaccharide and disaccharides described above. In some foods, carbohydrate makeup is almost entirely sugar. For example, a tablespoon of fruit preserves, sweetened only with fruit juices, has 9 of its 10 grams of carbohydrates in sugar. Breads and pastas, on the other hand, have high polysaccharide contents. Fiber helps the body digest food. Soluble fiber, combined with a lowfat diet, may reduce levels of the bad cholesterol. The recommended dietary allowance for fiber is 25 grams. Generally, grains, such as oat, wheat, and rice products, are good sources of fiber, as are some vegetables. But some foods that might seem as though they would be high in fiber, such as cereals, in fact have very little. High-sugar cereals often have just 1 gram of fiber; a high-fiber hot wheat cereal could have 5 grams; and a 100% bran cereal could have 8 grams or more. Some fruits, such as an apple (3.5 grams), a banana (2.4 grams), three prunes (3 grams), and a half grapefruit (3.1 grams) also have high fiber content. Sugar is also at the top of the pyramid because it's high in calories and low in nutritional content. Taking in more calories without adding more physical activity will cause you to gain weight. If you fill up on sugary foods, you'll be less likely to eat a more balanced diet. All carbohydrates eventually break down into sugars in your body. The difference is that complex carbohydrates do so more gradually, providing energy over a longer period of time. Complex carbohydrates also contain other nutrients not contained in simple sugars. That's particularly true of "empty" calories, such as soft drinks and candy. Carbohydrates provide the body with energy and they are the most plentiful of all the nutrients. They are mainly found in plant foods, such as potatoes and rice. The carbohydrate group consists principally of sugar, starch, dextrin, cellulose, and glycogen, substances that constitute an important part of the human diet and that of many animals. The simplest of them are the simple sugars, or monosaccharide, which contain either an aldehyde or a ketone group. The most important is glucose. Two monosaccharide molecules joined together by an oxygen atom, with the elimination of a molecule of water, yield a disaccharide, of which the most important are sucrose (ordinary cane sugar), lactose, and maltose. Polysaccharides have enormous molecules made up of one type or several types of monosaccharide units-about 10 in glycogen; 25 in starch; and 100 to 200 in cellulose (www.encarta.msn.com%A0/encyclopedia_ 761577934/Carbohydrate.html).. Types of carbohydrate There are three types of carbohydrates: Sugar Sugar is a simple carbohydrate and can be easily absorbed and digested by the body, providing instant energy. Sugars are found in honey, fruit, sugar cane, and sugar beet. Starch Starch is a complex carbohydrate and it takes the body longer to gain energy from it than from sugar. This is because it has to be broken down into smaller molecules first. Starch provides slow-releasing energy. It is found in cereals, pulses, nuts, vegetables, pasta, and bread. It is often referred to as a staple food, as it is a main element of our diet. Most starch products have to be cooked before they can be digested, unlike sugars, which can be eaten raw. Non-starch polysaccharides Non-starch polysaccharides (dietary fiber) cannot be digested by humans because the molecules are too complex. However, fiber is good for the body as it flushes out the digestive system, helping to prevent constipation and ridding the body of toxins. It also gives a feeling of fullness because it acts like a sponge. Fiber is found in fruit, vegetables, bran, brown bread, brown rice, and many other products. Refined products, such as white rice, tend to lack dietary fiber. Dietary goals Excess carbohydrate can lead to obesity because the body stores the unused energy by producing fat. Nutritionists recommend that we should eat more dietary fiber and cut down on high-sugar foods such as cakes, biscuits, chocolate, fizzy drinks, and ready-made desserts. Sugars can also lead to tooth decay. We should eat more fresh and dried fruits and use artificial sweeteners, where possible, to avoid tooth decay (The Hutchinson Encyclopedia, 2003). Carbohydrates in baking Starch does not dissolve in a room-temperature liquid. The liquid must be heated to enable the starch particles to swell and rupture. At 60C the starch absorbs liquid. The particles soften and swell up to five times their original size. On further heating (up to 80C) the particles rupture, releasing the starch. This effect is used in thickening sauces or creating a crumbly texture in bread, sponges, and biscuits. Sugars caramelize on baking, giving color to the dish as well as flavour. Sugars also aerate food by trapping air inside fat particles, helping the product to rise. Sugar acts as an activator in bread-making, giving the yeast energy for fermentation. It can also stabilize a product, for example meringue, by strengthening the protein in the egg white (The Hutchinson Encyclopedia, 2003). Uses and Function of Carbohydrate Carbohydrates are used in the manufacture of fabrics, photographic film, plastics, and other products. Cellulose, a carbohydrate, can be converted into viscose rayon, acetate rayon, and paper products. Cellulose nitrate (nitrocellulose) is used in the production of motion picture film, cement, guncotton, celluloid, and similar kinds of plastics. Starch is used in the preparation of foods for livestock and humans; pectin, a gelling agent; gum Arabic; and agar, used in the production of adhesive materials, sizing materials, and emulsions. Gum Arabic is also used in demulcent medicines. Agar, a constituent of some laxatives, is also used as a thickening agent in food and as a medium for bacterial culture. Hemicellulose is used to modify paper during its manufacture. The carbohydrate dextran is a polysaccharide used in medicine as a blood-plasma-volume expander to counteract acute shock; another carbohydrate, heparin sulphate, is a blood anticoagulant (www.encarta.msn.com%A0/encyclopedia_ 761577934/Carbohydrate.html).. Carbohydrates have many uses in baking: They can be used to thicken sauces They can created a crumbly texture in bread, sponges, and biscuits They give color and flavour to a dish They aerate food They can be used as a stabilizer. Summary and the function of Carbohydrate There are three types of carbohydrate: Sugars: these provide an instant source of energy but can cause tooth decay Starches: these provide slow-release energy and generally have to be cooked before they can be eaten Non-starch polysaccharides (dietary fiber): these cannot be digested by the body but keep the digestive system healthy Eating too many carbohydrates can lead to obesity because the unused energy is stored as fat (The Hutchinson Encyclopedia, 2003). Reference: www.encarta.msn.com%A0/encyclopedia_ 761577934/Carbohydrate.html. The Hutchinson Encyclopedia, 2003. Carbohydrates are needed in the body to carry out certain functions. Describe the different types of carbohydrates and their uses in nutrition and baking. Foster-Powell, K., Brand Miller, J. (1995), International tables of glycaemic index. American Journal of Clinical Nutrition. 62. Read More

 

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