Sunday, April 15, 2012

The Study of Metabolism: Biological Thermodynamics


The three Laws of Thermodynamics govern the universe and everything it contains. These three laws are fundamental to our understanding of the universe, and in this particular case they help us to understand the various biological processes.
The First Law states that the total energy of the universe is always constant. Energy could neither be created nor destroyed, it could only be transformed. This is also known as the Law of conservation of energy.
The Second Law states that in any open system the total entropy always increases, in simpler terms the universe is always becoming more chaotic, disorderly.
The Third Law states that at all motion stops at when temperature reaches absolute zero, the entropy would also be zero.
When understanding metabolisms only the first two laws are of interest to us.
 Every metabolic process whether it is hunting for food, cellular respiration, or reproducing offspring requires energy. Since energy could not be created at will according to the First Law, organisms must obtain energy from somewhere. Plants take light energy from the sun and transform it into chemical energy in the form of carbohydrates. Animals take the chemical energy stored in plant and transform it into kinetic energy and heat. The First Law of Thermodynamics explains why I need to eat in order to do anything, but why do I need energy when I am not moving, not thinking, not digesting? This is where the Second Law of Thermodynamics comes in. Every spontaneous event always increases the entropy of the system, which means the entropy level in our body always increases just by existing in the universe. This means our body gets more disorganized, our cells breakdown, and we age. Our body is like a china plate, and time, which could be understood as increase in entropy is like a hammer that breaks the plate. The plate shatters into many pieces as it follows the Second Law of Thermodynamics. We try to glue the pieces back together but no matter how hard we try the plate would not return to its unbroken state. As time goes on and the plate is shattered again and again, it will eventually reach a state beyond repair. Our body is constantly undergoing wear and tear and it is constantly being repaired which of course requires energy and nutrient. Just like the china plate our body will reach its limit one day and then we die. Just as a side note this is also the reason why our universe will end in 500 billion years. But what can you do, it is the way of the universe.

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