Digestion Essay Example | Topics and Well Written Essays - 750 words

Digestion - Essay Example The digestion of carbohydrates starts from the mouth where the teeth and tongue have their specific functions. The teeth are used for the process of grinding the food which helps in splitting down the large carbohydrate molecules into smaller ones known as disaccharides and monosaccharides. Saliva has a special enzyme known as amylase which helps in breaking down the bonds found in the molecule of starch. The carbohydrates then reach the stomach where the process of digestion stops because of the acidic environment found there. These molecules are then pushed into the small intestine where the pancreatic juice neutralizes the hydrochloric acid of the stomach so that the enzymes can work on these molecules. Pancreatic amylase and salivary amylase start working in the small intestine and hydrolyze the large carbohydrate molecules into oligosaccharides. These oligosaccharides are then digested by oligosaccharidases which helps in forming disaccharides. These disaccharides are then diges ted by disaccharidases into basic units which can be then absorbed. Hexoses and pentoses are easily absorbed in the small intestine by the transporters through a symport mechanism. After absorption into the blood stream the carbohydrates are processed in the liver to form glycogen or form glucose from other monosaccharides such as fructose or galactose. The monosaccharides are also used to form the nonessential amino acids inside the body (Ganong 2005) The digestion of the proteins starts in the stomach where the enzyme pepsin works on the proteins to break the peptide linkages formed between amino acids. The low pH in the stomach helps to maintain the functionality of the enzyme pepsin. The remnants of digestion are then moved to the small intestine where pancreatic enzymes act on them. Trypsin, chymotrypsin and elastase act on the remnants to digest them further so that they can be absorbed. These enzymes break some of the molecules into the basic units of amino acids. It is throu gh sodium dependent or independent transport mechanisms that the amino acids are transferred into the intestinal lumen. Most of the amino acids are absorbed in duodenum and jejunum whereas only a small amount is absorbed in the ileum. After the absorption the amino acids are moved into the muscle cells or liver where they can be used to form protein or glucose for energy purposes (Ganong 2005) The digestion of lipids starts from the stomach by two enzymes namely lingual lipase and gastric lipase. Gastric lipase is usually inactive under normal conditions but the lingual lipase helps in digesting about 30% of the lipids in the stomach. A major portion of the lipid digestion starts in the duodenum when pancreatic lipase acts on the lipids. This pancreatic lipase helps in forming fatty acids and 2 monoglycerides. Because of the insoluble nature of fats it becomes very difficult for them to cross the luminal membrane of the small intestine. It is here that the role of bile salts comes i nto play when it emulsified the fats into micelles. These micelles then move down the concentration gradient carrying the triglycerides into the enterocytes. After the absorption of fats they are transported to the liver where they are processed to be used by the adipocytes for storage or cardiac muscles for energy (Ganong 2005) Vitamin A, D and B12 are all found in the meal consumed by Jane. The vitamins do not have to be digested in order to get absorbed. Vitamin B 12