Which disaccharide is commonly known as milk sugar?

Lactose is commonly known as milk sugar because it is the primary sugar found in milk and dairy products. It is a disaccharide composed of two monosaccharides: glucose and galactose. The presence of lactose in milk is crucial for the nutrition of infants, as it provides a source of energy and facilitates the absorption of certain minerals like calcium.

Maltose, on the other hand, is formed from two glucose units and is typically found in malted foods and beverages. Sucrose, commonly known as table sugar, is made up of glucose and fructose and is found in many plants, being particularly abundant in sugarcane and sugar beets. Glucose is a monosaccharide that serves as a primary energy source for the body's cells but is not a disaccharide, thus not fitting the description of a sugar found in milk.

The identification of lactose as the sugar in milk highlights its unique role in dairy products and its specific composition, distinguishing it from other disaccharides.