Case study- Lactose Intolerance

Case details

A 30- year-old Asian male presents with bloating, abdominal cramps, and diarrhea. He states that he develops these symptoms whenever he drinks milk or eat dairy products. He is diagnosed with lactose intolerance, a common condition in which lactose is not digested normally and accumulates in the gut. Lactase converts lactose into :

A. Two glucose molecules

B. Glucose and Fructose

C. Glucose and Galactose

D. Fructose and Galactose

E. Sucrose and Maltose

Answer- The correct answer is C- Glucose and galactose.

Lactose is a disaccharide made up of Galactose and glucose residues  linked together by beta 1-4 glycosidic linkage. Lactose is hydrolyzed by lactase to its components.

lactose structure


Figure-1- Structure of Lactose

Two glucose residues are the hydrolytic product of either Maltose or Isomaltose. Maltose contains two glucose residues linked together by Alpha 1-4 Glycosidic linkage (figure-2) whereas isomaltose contains two glucose residues linked together by alpha 1-6 glycosidic linkage (figure-3)


Figure-2- Structure of Maltose


Figure-3 -Structure of Isomaltose

Glucose and Fructose are constituents of Sucrose (figure-4) which is hydrolyzed by Sucrase.


Figure 4- Structure of Sucrose

Fructose and galactose are not the hydrolytic products of any disaccharide.

Similarly sucrose and maltose are not the hydrolytic products, they are themselves disaccharides, and they are further digested by sucrase and maltase to their constituents.

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