Nutrition Essay Example | Topics and Well Written Essays - 1500 words

Nutrition - Essay Example These enzymes hydrolyze the long peptides of the chyme to short peptides containing only 2 or 3 amino acids. Any unaffected protein particles that have escaped the gastric juice are digested. The ability of the intestine to digest, not only gastric peptides, but also intact proteins, makes possible the nutrition of people with achylia gastrica and even of persons who have had the stomach completely removed. The soluble digestive products then diffuse into the bacterial cell and are used. Protozoa usually sweep food particles and water into their bodies, at a fixed or a changed position; and these food vacuoles constitute temporary "stomachs" in which the digestion proceeds. Metazoa have permanent digestive organs, most elaborate in the mammals. Man's digestive system, or alimentary canal, is a continuous passage through the body, from mouth to anus, with special extensions into accessory secreting organs (glands) (Lipski, 2004). 2. Whenever an organism consumes food in the solid state, this must be brought into solution before it can be utilized. It is necessary, therefore, that such solid food be digested. In some organisms digestion may occur outside of the body, and this may constitute an important adaptation for those animals which are in the habit of eating animals larger than themselves (Lipski, 2004). Ordinarily, however, food is taken into the body and digested there. Digestion may occur in cavities of special organs such as the stomach or intestine, or it may occur within the protoplasm of cells. The latter type of digestion obviously takes place in protozoa. In organisms such as paramecium or ameba the ingested food is enclosed in a food vacuole, which serves the same purpose as the stomach or intestine of a complicated metazoan. Within the food vacuole the solid food particle is brought into solution. It must not be thought, however, that intracellular digestion is confined to protozoa. Moreover, in some animals rather higher in the evolutionary scale, there is also a certain amount of intracellular digestion (Holford 2005). These phagocytic cells even enter into the lumen of the stomach or intestine, ingest particles of food there and then carry these food particles back into the tissues and digest them there. Such intracellular digestion, however, is a primitive character and it does not occur to any extent in higher animals such as the insects and vertebrates. In the conversion of solid food to a state of solution, enzymes play the leading role. It will be necessary, therefore, to consider the subject of enzymes and the nature of enzyme action. It should be strongly emphasized, however, that enzymes are not concerned only with digestion, but that they are essential factors in all of the chemical activities of the organism (Lipski, 2004). The living organism is essentially a chemical engine, dependent for its growth, maintenance and energy on chemical reactions. These reactions are controlled by catalysts. One of the most striking achievements of modern biology and biological chemistry is the isolation of more and more of these catalysts so important for the vital process. Once isolated, it is possible to study their behavior in test tubes or other suitable containers. In other words, one can detach from the living material certain non-living substances capable of causing or promoting the complex chemical transformations which constitute a major part of the mystery of protoplasm. The substance