Question

A marathon runner needs sustained energy for a long race. Which biomolecule would provide the MOST efficient long-term energy storage?
Question 4 options:

Proteins build and repair muscle tissue during extended exercise

Carbohydrates provide quick energy for immediate use during exercise

Nucleic acids control gene expression during periods of stress

Lipids store more than twice the energy per gram than alternatives

Answer 1

Lipids store the most efficient long-term energy. Fats yield about 9 kcal/g (more than twice the ~4 kcal/g from carbohydrates or proteins), are densely packed (hydrophobic, no water bound), and are the primary long-term energy reserve once short-term glycogen stores are depleted.