Glucose For Later Use As Energy example essay topic

The Chemistry of Carbohydrates The chemistry of carbohydrates most closely resembles that of alcohol, aldehyde, and ketone functional groups. As a result, the modern definition of a carbohydrate is that the compounds are polyhydroxy aldehydes or ketones. The chemistry of carbohydrates is complicated by the fact that there is a functional group (alcohol) on almost every carbon. In addition, the carbohydrate may exist in either a straight chain or a ring structure. Ring structures incorporate two additional functional groups: the and acetal. A major part of the carbon cycle occurs as carbon dioxide is converted to carbohydrates through photosynthesis.

Carbohydrates are utilized by animals and humans in metabolism to produce energy and other compounds. Carbohydrates are initially synthesized in plants form a complex series of reactions involving photosynthesis. They store energy in the form of starch or glycogen in animals and humans. They provide energy through metabolism pathways and cycles.

Carbohydrates also supply carbon for synthesis of other compounds. (Berdanier, Pgs 45-47). Metabolism occurs in animals and humans after the ingestion of organic plant or animal foods. In the cells a series of complex reactions occurs with oxygen to convert.

For example glucose sugar into the products of carbon dioxide and water and energy. This reaction is also carried out by bacteria in the decomposition / decay of waste maters on land and in water. Combustion occurs when any organic material is reacted or burned in the presence of oxygen to give off the products of carbon dioxide and water and energy. The organic material can be any fossil fuel such as natural gas (methane), oil, or coal. Other organic materials that combust are wood, paper, plastics, and cloth.

The whole purpose of both processes is to convert chemical energy into other forms of energy such as heat. All carbohydrates are made up of units of sugar (also called saccharide units). Carbohydrates that contain only one sugar unit (monosaccharides) or two sugar units (disaccharides) are referred to as simple sugars. Simple sugars are sweet in taste and are broken down quickly in the body to release energy.

Two of the most common monosaccharides are glucose and fructose. Glucose is the primary form of sugar stored in the human body for energy. Fructose is the main sugar found in most fruits. Both glucose and fructose have the same chemical formula (C 6 H 12 O 6). Disaccharides have two sugar units bonded together. For example, common table sugar is sucrose a disaccharide that consists of a glucose unit bonded to a fructose unit.

(Honeyman, Pgs. 66-69). Complex carbohydrates are polymers of the simple sugars. In other words, the complex carbohydrates are long chains of simple sugar units bonded together (for this reason the complex carbohydrates are often referred to as polysaccharides).

The potato actually contains the complex carbohydrate starch. Starch is a polymer of the monosaccharide glucose. (Honeyman, Pgs. 66-69). Starch is the principal polysaccharide used by plants to store glucose for later use as energy.

Plants often store starch in seeds or other specialized organs, for example, common sources of starch include rice, beans, wheat, corn, potatoes, etc. When humans eat starch, an enzyme that occurs in saliva and in the intestines called amylase breaks the bonds between the repeating glucose units thus allowing the sugar to be absorbed into the bloodstream. Once absorbed into the bloodstream, the human body distributes glucose to the areas where it is needed for energy or stores it as its own special polymer - glycogen. Glycogen, another polymer of glucose, is the polysaccharide used by animals to store energy. Excess glucose is bonded together to form glycogen molecules, which the animal stores in the liver and muscle tissue as an 'instant's our ce of energy. Both starch and glycogen are polymers of glucose, however starch is a long, straight chain of glucose units, whereas glycogen is a branched chain of glucose units.

Another important polysaccharide is cellulose. Cellulose is yet a third polymer of the monosaccharide glucose. Cellulose differs from starch and glycogen because the glucose units form a two-dimensional structure, with hydrogen bonds holding together nearby polymers, thus giving the molecule added stability. Cellulose, also known as plant fiber, cannot be digested by human beings therefore cellulose passes through the digestive tract without being absorbed into the body.

Some animals, such as cows and termites, contain bacteria in their digestive tract that help them to digest cellulose. Cellulose is a relatively stiff material, and in plants cellulose is used as a structural molecule to add support to the leaves, stem and other plant parts. Despite the fact that it cannot be used as an energy source in most animals, cellulose fiber is essential in the diet because it helps exercise the digestive track and keep it clean and healthy. Cellulose and starch provide an excellent example of the link between the structure and function of bio molecules. At the turn of the century, Emil Fischer suggested that the structure of an enzyme is matched to the substance on which it acts, in much the same way that a lock and key are matched.

Thus, the amylase enzymes in saliva that break down the linkages between glucose molecules in starch cannot act on the linkages in cellulose. (Robyt, Pgs. 120-128). Most animals cannot digest cellulose because they don't have an enzyme that can cleave linkages between glucose molecules. Cellulose in their diet therefore serves only as fiber, or roughage.

The digestive tracts of some animals, such as cows, horses, sheep, and goats contain bacteria that have enzymes that cleave these linkages, so these animals can digest cellulose. There is now a large amount of evidence that carbohydrates can improve the performance of athletes. During high intensity exercise, carbohydrates are the main fuel for the muscles. By consuming high levels of carbohydrate before, during and after training or an event, glycogen stores are kept well stocked. These stocks help the athlete to perform for longer and help their bodies sustain the effort. The vital role of physical activity in maintaining health and fitness in the general population is now recognized.

For those who want to keep fit and active, a well-balanced high-carbohydrate diet is recommended.

Bibliography

1. Berdanier, Carolyn D. Carbohydrate Metabolism. Washington, 1976.
2. Honeyman, John. Introduction to the Chemistry of Carbohydrates. Oxford, Clarendon, 1968.
3. Robyt, John F. Essentials of Carbohydrate Chemistry. New York, 1998.
4. Bradley, Ron. "The Basics of Carbohydrates". Eu fic Inc. Aug 9, 1998.
5. "Carbohydrates". Vision Learning. The National Science Foundation, 2003.