Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Desperate Need of Help

  1. Sep 24, 2006 #1
    Desperate Need of Help!!!

    I've done my homework (except one problem) and I want to make sure I am correct?

    1. What is the sign (delta G) for the folding process? Unfolding? How do you know?
    -(delta G) at low temp is positive and equilibrium will favor protein folding. At high temperature, delta G is negative and unfolding occurs because strong increase of change of entropy that lowers Gibbs free energy.

    2. What is the sign for (delta S) “ “
    -Unfolding (delta S) is positive and folding is negative because breaking of favorable interactions holding the folded protein will need input of energy , and delta H will increase also. When temperature increases, randomness increases and denaturation occurs at high temperature. Folding is in relation to decrease in randomness (at low temperature) and becomes more ordered.
    3. What will contribution of delta S to the free energy change be positive or negative? What does this mean?

    4. What are the main bonds and interactions that must be broken or disrupted is a folded polypetide is to be unfolded? Why does heat or ph cause unfolding?
    -H-bonds, disulphide, salt bridges, and hydrophobic interactions are disrupted. If heat is added, vibrational modes in the molecule will be excited and will disrupt hydrophobic interactions and dipole-dipole interactions and denature protein. If ph were to change, the protonation state of amino and carboxyal groups change and ionic bonds in the proteins disrupt and disrupts salt-bridges.
  2. jcsd
  3. Sep 24, 2006 #2


    User Avatar
    Staff Emeritus
    Science Advisor

    Biochemistry is not my area, although I do find it fascinating. Nevertheless, I found this. http://en.wikipedia.org/wiki/Protein_folding
    If a process if spontaneous, what is the sign on Gibbs free energy?

    http://ocw.mit.edu/NR/rdonlyres/Health-Sciences-and-Technology/HST-508Fall-2005/2258C576-52A7-4492-A812-896F02EF46B6/0/lecture_st2.pdf [Broken] pdf file.


    Last edited by a moderator: May 2, 2017
  4. Sep 24, 2006 #3
    Thank you very much!

    Can you interpret question 3 for me?:
    3. What will contribution of delta S (entropy) to the free energy change be positive or negative?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook