Carbohydrate Digestion Flashcards
Does any carbohydrate digestion occur in the mouth? Explain why/why not.
A small amount of carbohydrate digestion occurs in the mouth due to the presence of the alpha-amylase enzyme in the saliva. Alpha-amylase cuts some of the glycosidic bonds that connect the many sugar units within starch, producing shorter starch polysaccharides (and also maltose). The end result is the partial digestion of starch in the mouth.
The stomach acid contains the strong acid, hydrochloric acid (HCl). What role does the stomach play in carbohydrate digestion (if any)?
No digestion of carbohydrate occurs in the stomach due to the lack of carbohydrate digestion enzymes (not present). The harshly acidic environment of the stomach does not break the glycosidic bonds that connect the sugar units within the carbohydrates.
What enzyme(s) help facilitate carbohydrate digestion in the small intestine? What do these enzymes do to assist breaking down carbohydrates into smaller sugars (such as monosaccharides and disaccharides)?
The small intestine contains many enzymes that cleave the glycosidic bonds within different polysaccharide and disaccharide carbohydrates. Each carbohydrate requires a specific enzyme to cleave their glycosidic bonds that link the sugar units together in order to create smaller sugars (usually monosaccharides). For example, the lactase enzyme breaks down lactose (disaccharide) into one glucose unit and one galactose.
Why is it necessary to break carbohydrates down into monosaccharides in the small intestine?
Only carbohydrates in the monosaccharide form can be absorbed by the lining of the small intestine (via active transport), which allows the monosaccharides (glucose, fructose, galactose) to enter the blood. Carbohydrates in the disaccharide and polysaccharide from cannot be absorbed by the lining of the small intestine.
How are the carbohydrate digestion products are transported into the bloodstream? Where are the monosaccharides taken once in the blood?
Monosaccharides are absorbed by the lining of the small intestine (via active transport), which allows them to enter the blood. Once in the blood they are taken to the liver to be metabolised. Other cell types can also use the glucose produced in digestion (but not the fructose and galactose).
