Which group includes fats, oils, and waxes and is energy-rich?

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Fats, oils, and waxes are types of lipids. They’re energy-rich because their chemical structures store a large amount of energy in the long hydrocarbon chains; when lipids are broken down, they yield about 9 kilocalories per gram—more than carbohydrates or proteins, which provide about 4 kcal/g. Fats and oils are triglycerides, made of glycerol with three fatty acids; waxes are esters formed from fatty acids and long-chain alcohols. Lipids are largely nonpolar, so they don’t mix with water, allowing them to store energy densely without bringing along extra water weight. This dense energy storage is why animals use body fat as a long-term fuel reserve and seeds use oils to power germination, while waxes often protect surfaces and conserve water. In contrast, carbohydrates store energy too but with less energy per gram and are more hydrophilic, and proteins mainly serve structural and catalytic roles with energy as a secondary function.