Thermodynamics and Free Energy

Q1: The unfolding of regular secondary structure causes

A little increase in the entropy of protein

B large decrease in the entropy of the protein

C no change in the entropy of the protein

D large increase in the entropy of the protein

ANS:D - large increase in the entropy of the protein

No answer description is available.

Q2: Reactions that have positive standard free energy changes (ΔGo> 0) can be made to occur in cells by

A coupling them with exergonic reactions via a common intermediate

B manipulating the concentrations of products and reactants such that G/<0

C coupling them to the hydrolysis of ATP

D all of the above

ANS:D - all of the above

No answer description is available. 

Q3: The Standard Gibb's free energy, ΔG°, is

A the residual energy present in the reactants at equilibrium

B the residual energy present in the products at equilibrium

C the difference in the residual energy of reactants and products at equilibrium

D the energy required to convert one mole of reactants to one mole of products

ANS:D - the energy required to convert one mole of reactants to one mole of products

No answer description is available. 

Q4: During the unfolding reaction of a helix, breakage of each hydrogen bond requires about 2kJ/mol. This implies hydrogen bonds are

A much stronger in proteins than in water

B not reformed with water

C slightly weaker in proteins than in water

D slightly stronger in proteins than in water

ANS:D - slightly stronger in proteins than in water

What can be said about the thermodynamics of the unfolding of proteins as associated with H-bond breakage? Is it favorable?

I suppose entropy is increasing since the H-bonds are breaking, but at the same time the enthalpy term is +, so then the entropic effect here overweight the enthalpies effect and the reaction is favorable. It doesn't stop there because the energy being used to break the bonds is coming from an external source, so that is known as a coupling reaction thus why the breaking of the bonds can take place!

This has been an attempt for me to display what I have learned of the thermodynamics of biochemistry, and is not a credited answer, but a well articulated one using the laws of thermodynamics.

Q5: If the Standard Gibb's free energy, ΔG°, for a reaction is positive then

A the products will be favored

B the reactants will be favored

C the concentration of the reactants and products will be equal

D all of the reactant will be converted to product

ANS:B - the reactants will be favored

No answer description is available. 

Q6: If the enthalpy change for a reaction is zero, ΔG° is equal to

A TΔS°

B -TΔS°

C -ΔH°

D lnKeq

ANS:B - -TΔS°

Free energy of a chemical system is the energy that is available in doing work. It is the driving force that brings about a chemical change.



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