Why Catabolic Reactions Release Heat

Why do catabolic reactions release heat despite that breaking bonds absorbs heat?

Catabolic reactions involve the breakdown of complex molecules into simpler molecules, which releases energy. This energy is typically in the form of heat. While it is true that breaking chemical bonds requires an input of energy, catabolic reactions release more energy than is required to break these bonds. This excess energy is what leads to the release of heat.

To understand why catabolic reactions release heat, we need to consider the concept of bond energy. Bonds between atoms in a molecule store potential energy, which is often in the form of chemical bond energy. Breaking these bonds requires an input of energy, known as bond dissociation energy. This input energy is typically in the form of heat

However, when a complex molecule is broken down in a catabolic reaction, the newly formed simpler molecules have stronger bonds than the original molecule. The energy released during the formation of these new bonds is greater than the energy required to break the original bonds in the complex molecule. This energy difference is known as the net energy or the overall delta (Δ) energy

The excess energy released in catabolic reactions is typically in the form of heat. This is because heat is the most convenient form in which energy is dissipated or transferred. When a bond is broken, the energy is briefly stored in the molecules involved in the reaction. However, when new bonds form, the excess energy is released as heat. This heat is then transferred to the surrounding environment

In summary, catabolic reactions release heat despite the fact that breaking bonds requires energy because the overall energy released during the formation of new bonds is greater than the energy required to break the original bonds. This excess energy is released as heat, which is transferred to the surrounding environment

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