Explain First and Second Laws of Thermodynamics
First Law of Thermodynamics – Law of Energy Conservation
The first law states that energy cannot be created or destroyed; it can only be transformed from one form to another. In the context of biology, this implies that the total energy of a closed system remains constant, although it may change forms such as from chemical to thermal energy.
In biological systems, energy from nutrients (like glucose) is converted through metabolic pathways into usable forms such as ATP. During cellular respiration, chemical energy in glucose is transformed into ATP, heat, and mechanical energy. The energy input equals the total energy output, conforming to the first law.
Second Law of Thermodynamics – Entropy Increases
The second law states that every energy transformation increases the entropy (disorder) of the universe. In other words, energy spontaneously disperses unless constrained. Biological systems maintain order and structure by consuming energy and releasing heat, thus increasing overall entropy.
For example, in cellular respiration, glucose is broken down into carbon dioxide and water. While the cell gains useful energy (ATP), the overall process results in increased entropy in the environment. Despite cells being highly organized, they do not violate the second law because they are open systems exchanging energy and matter with their surroundings.
Biological Implications
- Living organisms require a constant input of energy to maintain order and carry out life processes.
- The second law explains why some reactions require energy input (endergonic) and why energy efficiency is never 100% due to heat loss.
- Thermodynamic principles underlie bioenergetics, enzyme activity, and metabolism.