Metabolism and the Law of Thermodynamics.

DEFINITIONS:

Catabolic Reactions: reactions that result in the breakdown of complex substances.
Anabolic Reactions: cells build complex substances from simpler subunits e.g: DNA from nucleotidessum of all anabolic and catabolic processes in a cell or organism
Metabolism: sum of all anabolic and catabolic processes in a cell or organism

First Law of Thermodynamics/Law of Conservation Energy: states that energy can neither be created nor destroyed. It may change from one form to another, but the energy in a closed system remains constant.

Second Law of Thermodynamics/Law of Entropy: states that when energy is transferred, there will be less energy available at the end of the transfer process than at the beginning. Due to entropy, which is the measure of disorder in a closed system, all of the available energy will not be useful to the organism. Entropy increases as energy is transferred.

Third Law of Thermodynamics/Absolute Zero: theoretical temperature (0K) at which entropy reaches its minimum value.

CONNECTIONS:

 It is important to keep in mind that the human body does not consume energy, it merely changes it from one form to another, in reference to the first law, where it can be concluded that energy is conserved. The Law of Entropy states that a highly ordered system, such as life, tends to become more and more disordered. The increase in entropy in the surroundings produced by the living system is always greater than the decrease in entropy obtained in the living system itself. For example, if one were to drop mass, its potential energy is transformed into kinetic energy, and then into heat, sound and light. As a result, the entropy of the surroundings (the universe) will increase. The change in entropy is a function of the energy transformed in the body. In other words, an exergonic reaction releases energy which would increase entropy while endergonic reactions would decrease entropy. Looking at it from a 'big picture' perspective, where the planet is considered a closed system, the entropy will always be increasing. Additionally, if the world reached a temperature of absolute zero, humans would cease to exist for all the bonds would be broken. Humans are nothing but bonds being held together... therefore, is there really a point in referring the third law to metabolism? If I must, it would be the point where all molecular motions would cease and the high temperature would render the enzyme useless, for they would not be able to function. Ultimately, this is how I think metabolism obeys the three Laws of Thermodynamics.