Digestion and Enzymes of Healthy Person - Assignment Example

Digestion and Enzymes Number Department Task Recommended Dietary (Daily) Allowance (RDA) tables give the amount of nutrients an individual of a particular age group, gender, occupation or health condition needs if they are to maintain sound health and reduce the risks of diet associated ailments. Nutritional requirements are different for each nutrient and also vary between individuals and life stages. Some nutrients are required in larger quantities than in others, for example, protein is needed in grams while vitamin C is needed in milligram quantities (Farrell & Nicoteri, 2007, 377). Young children for instance require more carbohydrates to meet their energy requirements at such times when they are physically active. More protein is additionally required to match the active growth by rapidly dividing cells. At this stage also, there is need to provide sufficient vitamins in general, in order to build a strong immune system. Iron and zinc levels such as in legumes are important to lower risks of allergic reactions. Adolescents equally require more carbohydrates and proteins to match their rapid growth rates and active lifestyles. An increase of calcium and iron intake is recommended for the growing bones. For the females who have started going through their menses, additional iron and fluid intake is highly required to aid in replacement of blood lost during menstruation (Farrell & Nicoteri, 2007, 411). Pregnant women require more than usual iron for efficient oxygen transport in the body, both for the mother’s and baby’s nourishment. Increasing vitamin C intake helps iron absorption from foods. If planning for a pregnancy, 400 micrograms of folate per day is recommended. An increase of daily folate intake to 600 micrograms during actual pregnancy is advised to avoid neural tube defects (like spina bifida). Increase in iodine for normal growth and development of the baby during pregnancy is additionally stressed. For lactating women, an excess of 750-1000 ml a day of fluids is required to reduce the risk of dehydration and constipation as a result of breastfeeding. There basically is an observed increase in recommended nutrient intake for lactating women to provide the nutrients necessary both for the mother’s maintained health and for the optimum nourishment of the baby (Farrell & Nicoteri, 2007, 418). For majority of adults, growth is over as focus now shifts on maintaining good health and active lifestyles. This means low saturated fats, sugars and salts to minimize risks of developing age and weight related diseases such as cardiovascular diseases and diabetes. However, certain occupations may demand a conventional shift of recommended dietary allowance. Such include those that require a lot of physical labor which may consequently mean a lot more energy foods. At old age, more calcium is required in the diet to maintain healthy bones and reduce risk of osteoporosis. In addition, with aging come bowel problems and so adequate water and fiber in diets ensures digestive system is working well. The ability to conserve water also decreases along with the perception of thirst. It is therefore important to keep more hydrated and consume more water (Farrell & Nicoteri, 2007, 700). Task 2 Definition of Terms Digestion generally refers to the process of breakdown of food into simpler forms. Mechanical digestion is the physical breakdown of food substances basically to increase surface area for further chemical action. Chemical digestion involves the use of enzymes to hydrolyze complex food substances into simpler absorbable forms. Ingestion refers to consumption of substance by organism/ taking food into the mouth. Absorption of food entails the passage of food molecules through the walls of small intestines into the bloodstream. Assimilation is the process of using absorbed foods in the functioning and building of living tissues. Egestion is the removal of undigested food from the body via the anus as faeces (Green, 2006, 1-18). The Alimentary Canal The human alimentary canal is along hollow tube 5-6 meters long running from the mouth to the anus. The alimentary canal along with numerous other organs such as the liver and pancreas constitute the digestive system. Parts of the lengthy canal are folded and coiled inside the abdomen to fit this significant length into the body. Alimentary canal has linings stained with mucous which helps food smoothly slide through without causing mechanical damage to the linings of the wall. This mucous produced by the cells lining the canal also constitutes a protective covering which prevents the digestive juices inside the lumen from digesting the living cells of the wall. Food is moved along the alimentary canal and contents mixed with contractions and relaxations of muscles found along the whole length of the canal producing waves. This phenomenon is termed peristalsis. The walls of the alimentary canal are composed of four distinct layers. These are the mucosa, the sub-mucosa, the muscularis externa and the serosa. The mucosa itself is further composed of three layers. The innermost is the epithelium which has cells that secrete mucous. The structure of the epithelium differs in various regions of the canal. Underneath the epithelium is a layer of connective tissue, the lamina propria. A third layer of smooth muscles called mucosa occurs beneath the lamina propria (Lennard & Gulliksen, 2009, 78). The sub-mucosa is composed of an open-textured stretchy tissue with a plethora of elastic fibers called collagen fibers constituting the areole connective tissue. The sub mucosa is highly vascularized with numerous additional nerves. The muscularis externa is made up of an innermost layer with fibers running around the tube called the longitudinal muscle. The serosa on the other hand is a very thin layer composed of connective tissue covered with a single layer of thin, smooth, closely fitting cells. Digestion Process of Meat Sandwich Meat sandwich, depending on the manufacturer or food joint recipe however, can contain almost all food types from carbohydrates, to proteins to fats, vitamins, fiber and so on. Upon ingestion, teeth are used to break up large pieces of the sandwich thus initiating mechanical digestion. Muscles of jaw move lower jaw up and down and from side to side grinding the teeth against the sandwich in the lower jaw against those in the upper jaw. The premolars and molars have ridges for trapping and crushing food during chewing. Mastication acts to increase the surface area of food and increase contact with enzymes thus improving the efficiency of chemical digestion. Three pairs of salivary glands secrete saliva (which has mucous, water and other components) into the mouth. Mucous mixes the food during chewing and loosely into a bolus while also making the bolus slippery and thus easier to swallow. Saliva has two important enzymes; amylase and lysozyme. The lysozyme annihilates several types of bacteria such as staphylococcus and streptococcus which can result in infections. Lysozyme also, along with the washing action of saliva and a small amount of hydrogen carbonate ions (which help neutralize acid on teeth) assist in reducing incidences of tooth decay. The enzyme amylase catalyses the breakdown of starch yielding maltose and small glucose chains linked together (Lennard & Gulliksen, 2009, 90). The food is then moved down the esophagus by peristalsis and upon reaching the stomach the sandwich is churned in strong rhythmic movements due to the thick muscle layers of the stomach’s muscularis externa. This churning continues the mechanical breakdown begun in the mouth and also mixes the sandwich with juices secreted in the stomach. The inner layer of the stomach wall (the mucosa) produces gastric juice which contains protease, lipase and hydrochloric acid (HCL). A slimy coat of mucous containing hydrogen carbonate neutralizes acid and protects the stomach walls from damage by the acid. The protease secreted is pepsin which is produced by glands known as the chief cells. Pepsin, which functions to digest (the meat) proteins into short amino acid chains, is secreted in an inactive form (to prevent it from digesting the proteins in the cells which produce it) then activated into pepsin once in stomach conditions (pepsin is only stable in acidic condition/ 2-3 pH range). HCL (secreted from parietal cells in the gastric glands), is responsible for creating such acidic conditions and further helps in destroying potentially dangerous microbes present in the food (sandwich). The lipase initiates the hydrolysis of triglycerides into fatty acids and glycerol. Gastric juice also contains the intrinsic factor which helps in absorption of B vitamin later in the ileum (Green, 2006, 345). The pyloric sphincter muscles then relax and food is released into the duodenum. It is within the duodenum and the ileum that most digestion and absorption occurs. The small intestines are highly coiled with folded surfaces to reduce speed of food flow/ allow time for efficient digestion and absorption. In the small intestines, the pancreas secretes pancreatic juice which contains hydrogen carbonate ions, amylase, trypsin, chymotrypsin, carboxypeptidase and lipase. These enzymes continue digestion of the food that was started in the mouth and stomach. Digestion is finally completed by the cells by the enzymes produced by cells on the villi surfaces and the foods conveniently remain on the surfaces awaiting absorption. The muscles of the mucosa contract and relax swaying the villi to increase contact between villi surfaces and food contents in the small intestines than if they were still. In the troughs between the villi in the duodenum are glands called the crypts of Lieberkuhn which secrets mucous and new villi. Brunner’s gland, deeper in the duodenum walls, secrete watery mucous which has hydrogen carbonate ions that neutralize the acidic chime moving into the small intestines from the stomach (Lennard & Gulliksen, 2009, 124). Structure and Function of the Villi The villi (small finger-like projections on the wall of small intestines extending into the lumen of the small intestines) and micro-villi which predominantly take part in absorption have certain characteristic features which adapt them to this function. The villi are small and numerous to increase the surface area of absorption. The villi themselves are covered by even smaller finger-like projections called the micro-villi which further increase surface area for absorption. The plasma membrane of the micro-villi contains numerous pumps which use ATP to actively transport molecules across the membrane and numerous protein channels which facilitate fast and efficient movement of nutrients through facilitated diffusion. In addition, the cytoplasm of the epithelial cells lining the villi has numerous mitochondria which provide a source of ATP for the pumps. The villi are also highly vascularized with a dense network of capillaries which enable quick and efficient absorption (Green, 2006, 365). Upon completion of digestion, the villi are bathed in a fluid with nutrient sub-units (which include monosaccharide, amino acids, nucleic acids, glycerol and fatty acids) which body cells require. These nutrient sub-units pass through the walls of the small intestines then enter capillaries which are embedded within the villi and connected to the general circulatory system which transports these nutrients to the tissues of the body in a process called absorption. The lymph vessels called lacteals are important in absorbing fats. Undigested and unabsorbed food remains are passed on into the colon/ large intestines. In the colon and caecum, much of the remaining water and sodium and chloride ions are absorbed into the blood. The colon is highly folded to increase the efficiency of absorption. The short straight section referred to as the rectum connects the colon to the anus where undigested food remains are released to the outside of the body (Green, 2006, 400). Task 3 Characteristics of Enzymes Enzymes are catalysts which speed up reaction rates by lowering the activation energy of a reaction. Hydrolysis of the eaten protein, for instance, would inevitably occur even without a catalyst but when digestive enzymes such as pepsin or trypsin are present hydrolysis occurs much faster to meet the biological demands of cells. Metabolism is a term used to denote the sum of all chemical reactions within a living organism. Catabolism is a chemical reaction that causes hydrolysis of complex organic molecules into simpler ones by enzyme action. Catabolism is often associated with the release of energy, for example, the conversion of starch into maltose by enzyme amylase. Anabolism, in contrast, is the build-up of simpler substances to form more complex molecules. Anabolic reactions usually require energy and include, for instance, DNA polymerase which repairs and rebuilds DNA (Boyer, Krebs & Sigman, 2013, 312). Enzymes are also substrate specific in that they recognize and bind to a single type of substrate or reactant. The specificity of enzymes can be explained by the lock and key theory of enzyme action where the lock represents and enzyme while the key is portrayed as the substrate. The lock (enzyme) can only be opened by a particular key (substrate). Even when different substrate molecules are present, only those that are of a shape complementary to the active site are able to bind with the enzyme’s active site. Like the lock, the enzyme can be reused severally as it remains chemically changed after the reaction (Boyer, Krebs & Sigman, 2013, 413). The catalytic behavior of enzymes can be regulated to achieve specific reactions. The cells contain numerous different molecules which could react with one another in a myriad of ways but only a small number of these reactions occur because the cells control the reactions that take place by regulating the action of enzymes. Enzymes are also neither altered in any way during reactions nor are they used up. In addition the reactions they catalyze are always reversible. Enzymes are affected by such condition as pH, temperature and substrate concentration. At very temperatures and pH levels (very low ph too) enzymes are denatured while they are inactivated at lower temperatures. They have optimal temperature and pH ranges. Substrate concentration is directly proportional to enzyme action, that is, the higher the substrate concentration, the higher the enzyme activity and vice-versa (Boyer, Krebs & Sigman, 2013, 500). References Boyer, P. D., Krebs, E. G., & Sigman, D. S., 2013, The Enzymes (3d ed.). New York: Academic Press, 312, 413, 500. Farrell, M. L., & Nicoteri, J. A., 2007, Nutrition (2nd ed.). Sudbury, MA: Jones and Bartlett Publishers, 377, 411, 418, 700. Green, J., 2006, Digestion. North Mankato, Minn.: Stargazer Books, 1-18, 345, 365, 400. Lennard, K., & Gulliksen, E, 2009, Digestion. London: Red Fox, 78, 90, 124. Read More