The Digestive, Respiratory, and Urinary Systems
Some individuals do not produce sufficient amounts of the enzyme lactase to digest the sugar lactose, present in milk and dairy products, and are referred to as “lactose intolerant”. Lactose is a disaccharide, which must be broken down by lactase into its constituent monosaccharides, glucose and galactose, before it can be absorbed. If not broken down, it remains in the small intestines and is passed along into the large intestine, a place it does not belong, with waste materials. The results can range from dehydration and diarrhea to intestinal cramps and bloating. The pain and bloating often experienced by the lactose intolerant after lactose ingestion are caused by intestinal bacteria that metabolize the lactose to which they are normally not exposed. Products of this fermentation include organic acids and various gases. Some products are available to allow lactose intolerant individuals to eat lactose containing products, and are meant to be ingested just before eating milk or dairy products.
What is the likely nature of the products that, if taken before lactose ingestion, will inhibit the symptoms of lactose intolerant individuals?
|A||They are likely antibiotics that kill the bacteria in the intestine so that they cannot metabolize the sugar.|
|B||They probably contain the enzyme lactase, which will end up in the small intestine and allow lactose digestion.|
|C||They are probably cocktails of various drugs that inhibit urination and help to ease the pain.|
|D||They are likely drugs that allow the small intestine to absorb undigested lactose.|
These supplements actually do contain the enzyme lactase; since it is a normal digestive enzyme, it will not be broken down by the proteases present in the digestive system as most other proteins would. Choice A would have far reaching consequences, as the bacteria of the colon are mutualistic and play an important role in homeostasis. Choice C is unlikely and unsupported by the passage. While choice D is tempting, only monosaccharides may ever be absorbed by the small intestines -- this has to do with their size and the lack of any machinery to transport them across the small intestinal wall.