Which of the following is a disaccharide?

ANS:A - Lactose

Lactose is a disaccharide sugar composed of two monosaccharides, glucose and galactose, linked together by a glycosidic bond. It is commonly referred to as milk sugar because it is primarily found in milk and dairy products. The chemical structure of lactose consists of a glucose molecule joined to a galactose molecule by a β1-4 glycosidic bond. This bond forms between the hydroxyl (OH) group on the carbon-1 of the glucose molecule and the hydroxyl group on the carbon-4 of the galactose molecule. Lactose is an important source of energy in the diet, particularly for infants who rely on milk as their primary source of nutrition. In the digestive system, lactose is broken down into its constituent monosaccharides, glucose, and galactose, by the enzyme lactase, which is produced in the small intestine. Once broken down, glucose and galactose can be absorbed into the bloodstream and used as fuel by the body's cells. However, some individuals may have a deficiency of the enzyme lactase, leading to lactose intolerance. In such cases, lactose cannot be properly digested, resulting in symptoms such as bloating, gas, and diarrhea after consuming dairy products. Overall, lactose plays a significant role in nutrition, particularly in infant feeding, but its consumption may need to be moderated or avoided in individuals with lactose intolerance.