![]() ![]() The end result of carbohydrate digestion is the production of a small selection of monosaccharides (Glucose, Galactose, or Fructose) which can be transported past the small intestine epithelium.The major enzymes include lactase, sucrase, and maltase (Maltose is a disaccharide released from starch which is composed of two molecules of glucose). The brush border of the small intestine epithelium possesses membrane-bound enzymes which further digest disaccharides into absorbable monosaccharides.Digestion begins in the oral cavity with salivary amylase and continues in the small intestine with pancreatic amylase. As mentioned, only starches are digested within the luminal fluid of the small intestine where they are broken down into monosaccharide and disaccharide units.Digestion of starch begins within the small intestinal lumen whereas digestion of short sugar chains occurs directly on the luminal surface of the small intestine epithelium just prior to absorption.The small intestine mucosa can only absorb monosaccharides and so digestion requires processing of these dietary carbohydrates into their individual component sugars. Although the normal human diet contains a substantial amount of cellulose, this carbohydrate cannot be digested and is thus not considered a dietary carbohydrate. The human alimentary tract can also absorb sucrose, a disaccharide composed of glucose and fructose, as well as Lactose, a disaccharide composed of glucose and galactose. The most important carbohydrate is starch which is composed of large, branched chains of sugars. The human gastrointestinal system can only absorb a few types of carbohydrates, and three contribute the most number of calories in a normal diet. ![]()
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