Lactose is composed of following two sugars:

Appeared in: BHU NO-2019

Explanation

Lactose is a disaccharide, a type of carbohydrate formed by the joining of two monosaccharides.
It is specifically composed of one molecule of glucose and one molecule of galactose.
This combination is often referred to as milk sugar because it is the primary carbohydrate found in the milk of mammals.
The enzyme lactase is necessary to break down lactose into glucose and galactose for absorption in the human intestine.

Option A: Mannose is a monosaccharide, but it does not combine with glucose to form the disaccharide lactose.
Option B: The combination of glucose and fructose forms sucrose, which is commonly known as table sugar.
Option D: This option is incorrect because sucrose is itself a disaccharide (composed of glucose and fructose). A monosaccharide (glucose) does not combine with a disaccharide (sucrose) to form lactose.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Composition of the disaccharide lactose as background academic context rather than a clinical decision trigger.
Understanding the composition of lactose is crucial for managing patients with lactose intolerance, a common digestive disorder caused by a deficiency of the enzyme lactase.
Nurses play a key role in educating patients with lactose intolerance about dietary modifications, such as avoiding or limiting milk and dairy products, and suggesting alternatives like lactose-free milk or lactase enzyme supplements.
What if? If a patient has galactosemia, a rare genetic metabolic disorder, they cannot properly metabolize galactose. In this case, the patient must avoid all dietary sources of lactose and galactose entirely, which is a much stricter and more critical dietary restriction than for lactose intolerance.

How to Approach the Question

This is a factual recall question from biochemistry.
First, identify the key term in the question, which is 'Lactose'.
The question asks for the two simple sugars (monosaccharides) that make up lactose.
Recall the composition of the three main dietary disaccharides: Lactose, Sucrose, and Maltose.
Match the components: Lactose = Glucose + Galactose.
Review the other options to confirm your answer. Glucose + Fructose = Sucrose. Glucose + Glucose = Maltose. This confirms that 'Glucose and Galactose' is the only correct choice.

Concept Tested & Keywords

QUM17BTJAjQdJe9p4nIrAn

E6 textbook of Applied Biochemistry and Nutrition & DieteticsHarbans Lal (pp 26-464 of 479) p. 15-17

E6 Nutrition Monika Sharma 3e p. 63-65

Practise the full BHU NO-2019

Attempt every question from this paper in a timed mock, then review the full solution for each one.