Why are fats the most energy rich macronutrients? Triglycerides have a much higher proportion of carbon-hydrogen bonds per gram molecular weight than carbohydrates. The overall processes of oxidative metabolism involves breaking the relatively weak carbon-hydrogen bonds and forming stronger carbon-oxygen and hydrogen-oxygen bonds. The principles of thermochemistry can help answer the question of why triglycerides possesses more food calories (9kcal/gram versus 4kcal/gram). In general, bonds with greater electronegativity difference tend to be stronger. Carbon hydrogen bonds are thermochemically weaker than carbon-oxygen bonds. They require less energy to break than the bonds being formed, which represents a net potential energy decrease. The principles of oxidation-reduction give a formal way to say the same thing. The weaker carbon-hydrogen bonds represent a reservoir of electrons which can ultimately participate in bonds with oxygen. While from a thermochemical perspective, we are breaking weak bonds and forming strong bonds. From an oxidation-reduction perspective, we say that oxygen is being reduced. The tendency of oxygen to form strong bonds is expressed in redox by its high reduction potential.

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