MCQ Detailed View

Fats are the most energy-dense macronutrients in the human diet. When metabolized, they release a large amount of heat energy that the body can use for physiological processes such as maintaining body temperature, muscle movement, nerve function, and other metabolic activities.

The energy released during the metabolism of nutrients is measured as the calorific value. For fats, the average calorific value is 39 kJ per gram (or approximately 9 kcal/g). This is significantly higher than carbohydrates and proteins, which release about 17 kJ per gram.

Chemically, fats are composed of long-chain fatty acids attached to a glycerol backbone. During metabolism, fats undergo oxidation reactions in the presence of oxygen to produce carbon dioxide, water, and energy:

$$\text{C₁₆H₃₂O₂ + 23 O₂ → 16 CO₂ + 16 H₂O + Energy}$$

The energy produced in this reaction is primarily in the form of heat, which is harnessed by the body to perform essential biological functions. The high energy yield of fats makes them an efficient storage form of energy in the body, stored in adipose tissue for long-term use.

Understanding the calorific value of fats is also important in nutrition science and diet planning. It helps calculate daily energy requirements, design balanced diets, and manage weight. Unlike carbohydrates, which provide quick energy, fats provide a sustained energy source due to their slow metabolism.

Therefore, when 1 gram of fat is metabolized, the human body releases 39 kJ of energy, making fats the most energy-rich macronutrient. This principle is a fundamental concept in physical chemistry applied to biological systems, combining thermodynamics and biochemistry to understand energy transformations in the human body.