Question

I got these multiple questions wrong, can anyone please help me why I got them wrong =( My answers are in bold, and were marked wrong

1. How do the two reagents used to separate peptide chains that are covalently linked via disulfide bonds function? Mercaptoethanol (oxidizes/reduces) the sulfurs and iodoacetate forms a (covalent/hydrophobic/ionic) interaction with them.

2. Differences at the PrP and the PrPSc proteins occur mainly at which protein structure level(s)?

A		Primary only
B		Secondary only
C		Secondary and Tertiary
D		Tertiary only
E		Quaternary only
F		Primary and Secondary

3. Anfinson explanation for his results on RNAaseA was that

A		Hydrophobic collapse has to happen before disulfide formation
B		Quaternary structure is unrelated to tertiary structure
C		Primary structure is largely unrelated to protein folding
D		Disulfide formation is the most important part of protein folding
E		Disulfide formation is the least important part of protein folding

Answer 1

1. Iodoacetate forms covalent interaction. It is used to give stable alkyl thio ether derivatives.

2. Difference in PrP and PrpC occurs at Secondary and Tertiary structures, therefore option C should be correct.

3. The correct option should be "E: Disulfide formation is the least important part of protein folding" because the take home message from the Anfinsen's experiment is : primary structure dictates, how the tertiary structure of the protein. As soon as polypeptide chain is synthesized, it exposes the hydrophobic residues patches collapses into core of the protein's three dimensional structure. The disulfide linkages are formed in the end.