Biochemistry : Regulation and Chaperonins

Study concepts, example questions & explanations for Biochemistry

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Example Questions

Example Question #1 : Regulation And Chaperonins

Proteins fold to their native state because __________.

Possible Answers:

Their native state is the most disordered state (highest entropy)

Their native state is the lowest energy state

The transition to their native state has a very high and positive 

Their native state is what they are trying to become

Correct answer:

Their native state is the lowest energy state

Explanation:

Proteins do not have maximum entropy in their native state. Folding requires order which decreases entropy in the system. The energy toll needed for this decrease in entropy is more than made up with by the increase in bonds formed when the protein folds into its native state. Therefore, the native state of a protein has the lowest energy. 

Example Question #2 : Regulation And Chaperonins

Which of the following statements about protein folding is incorrect?

Possible Answers:

DnaJ and DnaK are chaperones in E. coli that coat the unfolded protein to prevent aggregation.

Protein folding diseases usually occur when beta-sheets misfold and precipitate into alpha-helices.

Chaperones are proteins that help other proteins fold properly.

The hydrophobic collapse causes formation of protein secondary, tertiary, and native state structure in that order.

Correct answer:

Protein folding diseases usually occur when beta-sheets misfold and precipitate into alpha-helices.

Explanation:

Protein folding diseases usually occur when beta-sheets alpha-helices misfold and precipitate into alpha-helices beta-sheets. This can lead to aggregation of amyloid deposits in the brain and neuronal apoptosis. Creutzfeld-Jacob Disease (CJD) and bovine spongiform encephalopathy (BSE, or mad cow disease) are examples of protein folding diseases.

Example Question #3 : Regulation And Chaperonins

Proper folding of proteins often requires molecular chaperones. Which of the following is not true about molecular chaperones?

Possible Answers:

Their binding to unfolded proteins is a passive, energy-free process.

All molecular chaperones are proteins themselves.

All are also ATPases.

They help prevent hydrophobic segments of proteins from binding to each other.

Their size ranges from monomers to large multisubunit proteins.

Correct answer:

Their binding to unfolded proteins is a passive, energy-free process.

Explanation:

The correct answer is "their binding to unfolded proteins is a passive, energy-free process." All molecular chaperones work by repeatedly binding to and releasing hydrophobic segments of unfolded proteins. This process is not passive and requires energy from the hydrolysis of ATP, which is why all molecular chaperones are also ATPases. All chaperones are proteins and they range in size from monomers to large multisubunit proteins.

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