How does metabolism relate to thermodynamics?

Metabolism relates to thermodynamics as it involves energy transformations, obeying the laws of thermodynamics.

Metabolism is the sum of all chemical reactions that occur within an organism, including anabolic (building up) and catabolic (breaking down) processes. These reactions involve energy transformations, which are governed by the laws of thermodynamics.

The first law of thermodynamics, also known as the law of energy conservation, states that energy cannot be created or destroyed, only transformed or transferred. In the context of metabolism, this means that the energy organisms obtain from food is not created nor destroyed, but rather transformed into other forms of energy. For instance, the energy stored in glucose molecules is not lost during cellular respiration, but is transformed into ATP (adenosine triphosphate), the main energy currency of cells, and heat.

The second law of thermodynamics states that every energy transfer or transformation increases the entropy, or disorder, of the universe. In metabolic processes, this is observed as some of the energy from food is lost as heat, increasing the overall entropy. This is why all metabolic processes are not 100% efficient, as some energy is always 'lost' as heat, although it is not destroyed, in line with the first law.

The concept of Gibbs free energy is also crucial in understanding how metabolism relates to thermodynamics. Gibbs free energy is the energy associated with a chemical reaction that can be used to do work. A reaction with a negative Gibbs free energy is spontaneous and can release energy, such as the breakdown of glucose in cellular respiration. Conversely, a reaction with a positive Gibbs free energy requires an input of energy, like the synthesis of glucose in photosynthesis.

In summary, metabolism is a series of energy transformations that obey the laws of thermodynamics. The first law governs the conservation of energy in metabolic reactions, while the second law explains the increase in entropy and the inefficiency of energy transformations. The concept of Gibbs free energy further elucidates how energy is utilised or released in different metabolic reactions.