The 2nd law of thermodynamics states that “in any spontaneous process, the total entropy of the universe always increases”. Yet in biological systems there are processes where there is a decrease in entropy during a reaction. Give an example of a biological process where entropy decreases (words are fine, specific reactions are not necessary). Then explain how these processes do not violate the 2nd law of thermodynamics.
An example of a biological process where entropy decreases is the process of protein folding. During protein folding, a linear chain of amino acids spontaneously folds into a specific three-dimensional structure. This folding process involves the decrease in the randomness (entropy) of the amino acids, resulting in a more ordered and structured protein.
However, this process does not violate the second law of thermodynamics because the total entropy of the universe still increases in this scenario. While the entropy of the protein decreases during folding, the surrounding environment experiences an increase in entropy. This increase is due to the release of heat energy and the movement of water molecules as the protein interacts with its surroundings.
In other words, although there is a localized decrease in entropy within the protein, the overall change in entropy for the system (protein + surroundings) is positive. The second law of thermodynamics focuses on the total entropy change of the entire system, and in this case, it is balanced out by the increase in entropy of the surroundings.
An example of a biological process where entropy decreases is the formation of a protein. During protein synthesis, amino acids are joined together in a specific sequence to form a protein molecule. This process involves the ordering and arrangement of amino acids in a highly specific and organized manner, resulting in a decrease in the entropy of the system.
Although this may seem to contradict the second law of thermodynamics, it is important to consider the entire system, including the surroundings. The decrease in entropy within a biological system, such as protein synthesis, is actually accompanied by an overall increase in entropy of the universe.
To explain this, we need to consider the concept of open systems. Biological systems are not isolated, but rather interact with their surroundings, exchanging energy and matter. In the case of protein synthesis, energy is provided by the breaking of ATP (adenosine triphosphate) molecules, which releases energy and is necessary for the ordering of amino acids. This energy transfer to the system leads to an increase in the entropy of the surroundings, compensating for the decrease in entropy within the system.
Additionally, the second law of thermodynamics focuses on the overall change in entropy, rather than the change in a particular subsystem. The ordering and decrease in entropy within biological systems are possible because they are coupled with energy inputs and the increase in entropy elsewhere in the universe.
In summary, biological processes that appear to decrease entropy, such as protein synthesis, are not in violation of the second law of thermodynamics. They are accompanied by energy inputs and an overall increase in entropy of the universe, satisfying the principles of the law.