Which one of the following is a major protein present in human milk?

BHU NO - 2015

Biochemistry & Nutrition

Easy

Appeared in: BHU NO - 2015

Explanation

Human milk protein consists of approximately 60% whey and 40% casein, making it whey-dominant.
Lactalbumin (specifically alpha-lactalbumin) is the most abundant single protein within the whey fraction.
This high proportion of easily digestible whey protein is a key nutritional advantage of human milk for infants, providing essential amino acids for growth.
The whey proteins form a soft, flocculent curd in the infant's stomach, which is digested more easily and rapidly than the hard, rubbery curd formed by casein.

Option B: Beta-lactoglobulin is a major whey protein in cow's milk and a common allergen. It is not present in significant amounts, if at all, in human milk.
Option C: Casein is a major protein group in human milk, constituting about 40% of the total protein. However, human milk is characterized by its higher whey-to-casein ratio (60:40), making whey proteins collectively more abundant. Cow's milk is casein-dominant (80:20).
Option D: Lactoferrin is a vital protein in human milk known for its iron-binding and antimicrobial properties, contributing to the infant's immune defense. However, it is present in smaller quantities compared to lactalbumin.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain The primary protein composition of human breast milk as background academic context rather than a clinical decision trigger.
The whey-dominant nature of human milk results in softer, more easily digestible curds in the infant's stomach, reducing the likelihood of colic, constipation, and other digestive issues.
Understanding this difference is crucial for nurses when educating new mothers about the benefits of breastfeeding and explaining the composition of infant formulas, which are often modified to mimic the whey-to-casein ratio of human milk.
What if? If an infant is fed unmodified cow's milk, the high casein content (80%) and different protein structure can lead to gastrointestinal distress, an increased renal solute load on immature kidneys, and potential allergic reactions.

How to Approach the Question

This is a factual recall question about infant nutrition.
First, identify the core of the question: the main protein component of human milk.
Recall the two main classes of milk protein: whey and casein.
Remember the fundamental difference between human and cow's milk: human milk is whey-dominant (approx. 60% whey, 40% casein), while cow's milk is casein-dominant (approx. 20% whey, 80% casein).
Evaluate the options based on this knowledge. Lactalbumin is the primary protein in the whey fraction. Casein is the other major group but is less abundant than whey overall. Lactoferrin is a minor protein by quantity, and lactoglobulin is characteristic of cow's milk.
Conclude that since human milk is defined by its high whey content, and lactalbumin is the main whey protein, it is the best answer among the choices.

Concept Tested & Keywords

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E6 Textbook of Biochemistry for medical StudentsDM Vasudevan Part 2 — Subpart A (pp 1-239 of 478) pp. 98-100, 101-103

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