# How do the first and second law of thermodynamics adhere to breakdown of glucose?

I know the first law is energy can only be converted from one form to the other, therefore in the breakdown of glucose 40% potential energy is converted to ATP and 60% is converted to thermal and unusable.

Does the second law adhere to the breakdown of glucose? Isn't it just the same as the first?

• I'm not sure what you're asking. The first law states that total energy in a closed system is constant, whereas the second law states that systems tend toward an increase in entropy. I don't understand how your question relates to these topics, but the laws of thermodynamics have yet to be violated, even in biology. Oct 31, 2013 at 2:00
• Second law adheres to all spontaneous natural processes, including all biochemical transformations occurring spontaneously. Oct 31, 2013 at 2:13

$$\Delta G = \Delta H - T\Delta S\leq0$$ That is, for a reaction to be favorable, the change in Gibbs free energy from the initial state (glucose) to the final state (carbon dioxide, water, and energy) must be negative. This equation is valid for systems at constant temperature and pressure, which is assumed to be satisfied in biological systems. According to Wikipedia, $\Delta G$ for the breakdown of glucose is negative, $\Delta G = -2880$ kJ/mol.