Question

Lactose intolerance is observed in individuals with deficiency of the enzyme ________________.

• A. Galactokinase
• B. Lactose-1-phosphatase
• C. Alpha lactose hydrolase
• D. Beta galactosidase

Hint:

Lactase is a specific type of \(\beta\)-galactosidase.
Its role is to split lactose into glucose and galactose.
Without it, lactose cannot be absorbed, leading to intolerance.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Lactose is the primary sugar present in milk and must be digested in the small intestine before it can be absorbed into the bloodstream.
Lactose digestion requires the enzymatic hydrolysis of the disaccharide into its constituent monosaccharides, glucose and galactose.

Step 2: Detailed Explanation:
The specific enzyme responsible for cleaving the \(\beta\)-1,4-glycosidic bond of lactose is \(\beta\)-galactosidase (commonly referred to as lactase).
In individuals with lactose intolerance, there is a deficiency or absence of active \(\beta\)-galactosidase in the brush border membrane of the enterocytes in the small intestine.
Because the lactose cannot be hydrolyzed, it remains undigested and passes into the large intestine.
In the colon, water-soluble lactose exerts osmotic pressure, drawing water into the intestinal lumen, while colonic bacteria ferment the lactose, producing gases (such as hydrogen, carbon dioxide, and methane) and short-chain fatty acids.
This results in symptoms like abdominal pain, bloating, flatulence, and diarrhea.
Therefore, the deficient enzyme is \(\beta\)-galactosidase.

Step 3: Final Answer:
Lactose intolerance is caused by a deficiency of the enzyme \(\beta\)-galactosidase.