What substrate does lactase act upon to produce glucose and galactose?

• A. Sucrose
• B. Lactose
• C. Maltose
• D. Fructose

Answer: (B)

Lactase is an enzyme specifically designed to break down lactose, which is a disaccharide sugar composed of two monosaccharides: glucose and galactose. By hydrolyzing the glycosidic bond between these two monosaccharides, lactase facilitates the conversion of lactose into its constituent sugars. This process is crucial for individuals who consume dairy products, as it allows for the proper digestion of lactose.

In contrast to lactose, other sugars listed do not serve as substrates for lactase. Sucrose, which consists of glucose and fructose, is broken down by the enzyme sucrase. Maltose, composed of two glucose molecules, is digested by the enzyme maltase. Fructose is a monosaccharide that does not require enzymatic hydrolysis from lactase, as it is already in its simplest form. Thus, the correct identification of lactose as the substrate for lactase highlights the enzyme's specific role in carbohydrate digestion.