A true statement about lipids is that they store energy.

A true statement about lipids is that they store energy.

• A. They store energy
• B. They are primarily enzymes
• C. They act as genetic material
• D. They are metals

Answer: (A)

Lipids store energy in a highly dense form, mainly as triglycerides. These molecules consist of glycerol linked to three fatty acid chains. The fatty acids are long, highly reduced hydrocarbon chains, so when they’re oxidized in metabolism, they release a lot of energy. Because lipids are nonpolar, they don’t dissolve in water, allowing them to pack into adipose tissue as liquid droplets and store a large amount of energy with relatively little space and weight. In human metabolism, fatty acids undergo beta-oxidation to acetyl-CoA, feeding the citric acid cycle and producing a high yield of ATP—about 9 kcal per gram, versus roughly 4 kcal per gram for carbohydrates. Beyond storage, lipids also contribute to membranes and insulation, but their role as a dense, long‑term energy reservoir is a defining feature. They are not enzymes, not genetic material, and not metals, which is why those statements don’t describe their primary function.

Lipids store energy in a highly dense form, mainly as triglycerides. These molecules consist of glycerol linked to three fatty acid chains. The fatty acids are long, highly reduced hydrocarbon chains, so when they’re oxidized in metabolism, they release a lot of energy. Because lipids are nonpolar, they don’t dissolve in water, allowing them to pack into adipose tissue as liquid droplets and store a large amount of energy with relatively little space and weight. In human metabolism, fatty acids undergo beta-oxidation to acetyl-CoA, feeding the citric acid cycle and producing a high yield of ATP—about 9 kcal per gram, versus roughly 4 kcal per gram for carbohydrates. Beyond storage, lipids also contribute to membranes and insulation, but their role as a dense, long‑term energy reservoir is a defining feature. They are not enzymes, not genetic material, and not metals, which is why those statements don’t describe their primary function.