**Question:** A man cannot digest carbohydrate. The enzyme deficient is

A. α-Amylase
B. β-Glucosidase
C. Maltase
D. Lactase

**Correct Answer:** D. Lactase

**Core Concept:**
Carbohydrate digestion and the role of specific enzymes are essential for understanding malabsorption syndromes. Carbohydrates are complex organic compounds that serve as the primary source of energy for our body. They are broken down into simpler sugars in the small intestine by various enzymes.

**Why the Correct Answer is Right:**
Lactase is an enzyme produced by the intestinal lining (L cells) and catalyzes the hydrolysis of lactose, a disaccharide composed of glucose and galactose. In lactose intolerance, there is a deficiency of lactase enzyme, leading to the inability to break down lactose and its subsequent fermentation in the colon, causing symptoms like bloating, diarrhoea, and abdominal pain.

**Why Each Wrong Option is Incorrect:**

A. α-Amylase: This enzyme is responsible for the breakdown of polysaccharides (complex carbohydrates) into maltose, not lactose.

B. β-Glucosidase: This enzyme is involved in the breakdown of disaccharides like maltose into monosaccharides (glucose and maltotriose), not lactose.

C. Maltase: Maltase is involved in the hydrolysis of maltose, not lactose. Maltase deficiency would result in malabsorption of maltose, not lactose.

**Clinical Pearl:** Lactose intolerance is a common gastrointestinal disorder affecting millions worldwide. It is crucial to differentiate lactose intolerance from malabsorption syndromes like celiac disease, where carbohydrate malabsorption is a feature, and the diagnosis involves a combination of clinical, endoscopic, and histological findings.