Question

2nd law of thermodynamics. (a) Explain the second law of thermodynamics and use an example to illustrate why this law is true. (b) Given the 2nd law of thermodynamics, how is it thermodynamically possible that a protein can spontaneously fold given the inordinate number of conformations available to it in the denatured form and the limited allowable arrangements in the native form (i.e., ΔS < 0 for the protein folding process).

Answer 1

(a) Explain the second law of thermodynamics and use an example to illustrate why this law is true.

- 2nd law of thermodynamics states that in order for a process to be "spontaneous" it must always increase the ordr/entropy of the universe as a whole, not the system or surroundings, but the total addition.

- Example:

burning a liquid chemical will break bonds and make a very chaotic gaseous mix. Plenty of moles of gas are created. This is spontnaeous, clearly an ordered system such as a liquid + oxydant, forms more chaots, less ordered system.

(b) Given the 2nd law of thermodynamics, how is it thermodynamically possible that a protein can spontaneously fold given the inordinate number of conformations available to it in the denatured form and the limited allowable arrangements in the native form (i.e., ΔS < 0 for the protein folding process).

The only way a process is possibe, i.e. spontaneous is if it is:

dS universe > 0

which implies

dS universe > dSsystem + dSsurroundings

if dSsystem < 0

then ,

dSsurroundings >> dSsystem

meaning that this process is actually incrasing the surrounding's entorpy, via increase of temperature, this must be exothermic.