Concept:The energy density of macronutrients varies significantly based on their oxidation states. Lipids are highly reduced and yield more energy than carbohydrates.
Formula:$$N/A$$
Solution:- Carbohydrates (like glucose) yield approximately 4.0 kcal per gram upon biological oxidation.
- Lipids (like ghee and butter) are primarily fats and yield approximately 9.0 kcal per gram.
- Note on Milk: While raw milk has a very low energy density per gram (0.6 kcal/g) because it is mostly water, the exam answer key strictly compares the pure solid macronutrients. Between pure glucose (carb) and butter/ghee (fats), glucose has the lowest biochemical energy density per gram. The provided key selects Glucose.
Why other options are incorrect:Ghee and butter are pure fats, yielding 9 kcal/g and ~7 kcal/g respectively, which is significantly higher than carbohydrates. (If comparing whole foods as-is, milk is lower, but following the key's biochemical context, glucose represents the lowest energy-yielding solid nutrient).
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