Lactase deficiency is common in humans, particularly those of European descent. Without this enzyme, products containing the sugar lactose cannot be broken down. When lactose cannot be digested, it serves as an osmotic agent in the intestines resulting in abdominal distention and subsequent diarrhea.

The sugar we eat, or table sugar, is known as sucrose. It is a disaccharide made of one molecule each of glucose and fructose.

Fructose is "fruit sugar." It is a monosaccharide found in honey, fruits, and flowers. Glucose is "blood sugar." It is a monosaccharide that is (like the name suggests) found in our blood. Maltose is "malt sugar." It is a disaccharide formed from two molecules of glucose. It is found in seeds such as barley and is also produced when glucose is caramelized.

Most mammals are unable to digest beta glycosidic bonds, such as the bonds in cellobiose and lactose. Maltose and sucrose both are connected via alpha glycosidic bonds, and can be digested by mammals.

Note: Most mammals are unable to digest lactose after infancy. It is only through a genetic mutation that many humans now are able to ingest lactose well into adulthood.

Three common simple sugars are: glucose, fructose, and galactose. Combining these simple sugars leads to the formation of more complex sugar molecules. Glucose and fructose make sucrose. Glucose and galactose make lactose. Two glucose molecules make maltose.

Maltose is a disaccharide formed from two glucose molecules. Mammals use the enzyme maltase to digest maltose. Lactose is a disaccharide formed from one glucose and one galactose molecule. Mammals use the enzyme lactase to digest lactose. Sucrose is a disaccharide formed from one glucose and one fructose molecule. Mammals use the enzyme sucrase to digest sucrose. Mammals cannot digest cellulose because they do not have the necessary enzymes to do so in their digestive tracts.

Sucrose is a disaccharide that is made up of a glucose and a fructose molecule, bound by a glycosidic linkage. A disaccahridase, called sucrase, breaks down sucrose molecules into their component monosaccharides (glucose and fructose), which can then by absorbed by the enterocytes in the small intestine.

Fructose is a monosaccharide that can be directly absorbed by enterocytes. Starch is a complex carbohydrate (polysaccharide) with many glucose molecules attached via glycosidic bonds.

A furanose is defined as a cyclical sugar structure with a five-membered ring. By contrast, a pyranose is a cyclical sugar structure with a six-membered ring.

"Oligo-" is a prefix which means "few." "Poly-" is a prefix which means "many." Just as the names suggest, combining a few monosaccharides leads to the formation of _oligo_saccharides. In the same way, combining many monosaccharides leads to the formation of _poly_saccharides.

Beta-linked polysaccharides are tougher to break down than alpha-linked polysaccharides. This feature makes beta-linked polysaccharides a key component in the cell walls of many bacteria such as peptidoglycan. For even more added structure, beta-linked polysaccharides can also pack into tight crystalline conformations (i.e., cellulose in celery stalks). Thus, all of the answer choices are correct.

Reduction of carbonyl groups in aldoses and ketoses gives sugar alcohols.