Question

Explain why fats contain $\mathbf{~}\mathbf{38}\mathbf{}\mathbf{kJ}$ of energy per gram, whereas carbohydrates contain$\mathbf{~}\mathbf{17}\mathbf{}\mathbf{kJ}$ per gram.

Short answer

Comparatively speaking to carbohydrates, fats are less easily oxidized. As a result, when fats oxidize, more energy is released.

Step-by-step solution

Definition of energy of fats and carbohydrates

Carbohydrates are a kind of carbohydrate that is utilized to generate energy (glucose). On the other hand, fats are also utilized for energy after being broken down into fatty acids.

Energy variation in fats and carbohydrates

Because fats are less oxidized than carbohydrates, they provide much more energy per unit mass when fully oxidized. Furthermore, lipids, such as triacylglycerols, are stored in their anhydrous state. In contrast, carbs, such as glycogen, bind to water in their physiological form, resulting in a larger weight with less energy.

Because lipids include a high percentage of C-H bonds, which store chemical potential energy more effectively than other molecules, fats have a substantially higher energy density than carbohydrates.

Hence, fats contain more energy per gram than carbohydrates.