MCAT Practice Exam – Complete Prep Resource 2026

Triacylglycerols (triglycerides) are a form of fat storage in the body, and they have a significantly higher energy density compared to glycogen, which is the storage form of glucose. The energy content of a molecule can be assessed based on its chemical structure and the number of available carbon-hydrogen (C-H) bonds, which release energy during metabolic processes.

Triglycerides are composed of three fatty acid chains linked to a glycerol backbone. They provide approximately 9 kcal per gram of fat due to the high number of C-H bonds, whereas glycogen, being a carbohydrate, provides around 4 kcal per gram. This reflects the fundamental difference in how these macromolecules store energy.

When comparing the energy yield, triglycerides can store nearly twice the energy per gram compared to carbohydrates when accounting for the hydration state of glycogen. Glycogen is stored with water molecules, making it heavier and thus less energy-dense on a weight basis. The number typically cited for triglycerides being more energy-dense than glycogen ranges from 6 to 8 times more, which can vary slightly based on specific conditions and types of fatty acids considered.

Therefore, stating that triglycerides hold 6 times more