Final answer:
The molecule joined with glucose to form the disaccharide lactose is galactose, and they are joined by a β-1,4-glycosidic bond.
Step-by-step explanation:
Lactose is a disaccharide formed by the joining of glucose and galactose. The bond that joins these molecules is a glycosidic bond. Lactose is commonly found in milk and requires the enzyme lactase for digestion. The absence of lactase activity leads to lactose intolerance.
The disaccharide lactose is composed of two monosaccharides: glucose and galactose. These two sugar molecules are joined together by a glycosidic bond, specifically a β-1,4-glycosidic linkage. During the formation of lactose, a dehydration reaction occurs, which results in the loss of a water molecule and the bonding of the monosaccharide units. This type of covalent bond is essential for the structural integrity of disaccharides and allows for their breakdown during digestion by enzymes such as lactase, which specifically targets the β-1,4-glycosidic bond in lactose.
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