Lipids can be stored in the body as a food resource because they are?

RUHS, Jaipur, M.Sc Nursing Entrance Exam-2015

Biochemistry & Nutrition

Medium

Appeared in: RUHS, Jaipur, M.Sc Nursing Entrance Exam-2015

Explanation

Lipids are defined by their insolubility in water (hydrophobic nature), a key property for their function in the body.
This insolubility allows lipids to be stored in a highly concentrated, anhydrous (water-free) state within adipose cells.
Anhydrous storage makes fat a much more compact and lightweight energy reserve compared to carbohydrates like glycogen, which are hydrophilic and stored with a significant amount of water.
As a result, fats provide a higher energy yield per unit of mass (approx. 9 kcal/g) and are ideal for long-term energy storage.

Option B: This is factually incorrect. Lipids are hydrophobic and insoluble in aqueous solutions. If they were soluble, they would be difficult to store in a concentrated form and would disrupt cellular osmotic balance.
Option C: While true that storage lipids (triglycerides) are rich in fatty acids, this describes their chemical composition, which is the source of their high energy content. It does not explain the physical property that allows for their efficient storage.
Option D: This is a tautological or circular statement. Saying lipids (fats) are 'fat soluble' does not explain their storage mechanism in a water-based organism. The term is typically used to describe other substances (like vitamins A, D, E, K) that dissolve in fats.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Biochemical properties of lipids for energy storage as background academic context rather than a clinical decision trigger.
The efficiency of adipose tissue in storing large amounts of energy is central to understanding weight management, obesity, and metabolic syndrome.
A nurse's understanding of this principle is vital for patient education on diet, explaining why high-fat foods contribute more to weight gain than equal amounts of carbohydrates or proteins.
What if? If lipids were water-soluble like glucose, the human body would need to be significantly larger and heavier to store the same amount of energy reserves, which would drastically impair mobility and survival. This highlights the evolutionary advantage of fat as a storage molecule.

How to Approach the Question

First, identify the core of the question: it asks for the specific property of lipids that makes them suitable for storage in the body.
Recognize that the body's internal environment is aqueous (water-based). An effective storage molecule must be compatible with this environment.
Evaluate each option based on fundamental biochemistry:
Option A (Insoluble): Insolubility would allow lipids to be compartmentalized and packed densely without interacting with water. This is a strong candidate for efficient storage.
Option B (Soluble): Solubility would cause the substance to disperse, making concentrated storage difficult and inefficient.
Option C (Rich in fatty acids): This relates to energy content, not the physical mechanism of storage.

Concept Tested & Keywords

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E6 Biochemistry U Satyanarayana— Part 1 (pp 26-420 of 840) p. 30-32

E6 Nutrition Monika Sharma 3e pp. 95-97, 100-102