aamc bio question

[PJS233006]

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I do not understand what is meant by the largest decrease in the entropic penalty. What I am thinking is entropy favors more disorder. So if it is a penalty, you want the choice to be something that will not form more ordered. But how does this all relate to water molecules?

 

[theonlytycrane]

there's an entropic penalty (bad thing) when a non-polar amino acid is at the water surface. If we replace leu (non-polar) with thr (polar), then the entropic penalty (bad thing) decreases (gets better).

 

[aldol16]

I do not understand what is meant by the largest decrease in the entropic penalty. What I am thinking is entropy favors more disorder. So if it is a penalty, you want the choice to be something that will not form more ordered. But how does this all relate to water molecules?

The entropic penalty refers to the ordered shell or clathrate of water molecules that must form around a hydrophobic residue on the protein surface. That's why proteins fold with hydrophobic cores - this reduces the entropic penalty that must be paid. Thus, you want something that will decrease the size of the clathrate shell.

 

[AWolfman]

You're basically looking for the answer that is better suited for its environment. Leucine is hydrophobic meaning it doesn't like to be around water, especially on the surface of the protein where you would normally find HydroPHILIC aa's. Substituting Threonine is better because it is charged (hydroPHILIC), therefore you reduce the entropy because it would rather be close to water than Leucine on the surface of the protein.

P.S. Your screenshot shows your name, so I would suggest blacking it out or taking the pic down.

 

[PJS233006]

You're basically looking for the answer that is better suited for its environment. Leucine is hydrophobic meaning it doesn't like to be around water, especially on the surface of the protein where you would normally find HydroPHILIC aa's. Substituting Threonine is better because it is charged (hydroPHILIC), therefore you reduce the entropy because it would rather be close to water than Leucine on the surface of the protein.

P.S. Your screenshot shows your name, so I would suggest blacking it out or taking the pic down.

Thank you! also thanks for letting me know that about my name I didnt even realize it.