Question 12 (4 points) Protein folding can be studied using a solution of purified protein and a denaturant (e.g. urea), a solvent that interferes with noncovalent interactions. Which of the following is observed after the denaturant is removed from the protein solution? 11 12 a) the polypeptide remains denatured. 14 15 the polypeptide adopts a new, different and stable conformation. 17 18 c) the polypeptide forms water insoluble aggregates and precipitates out of solution. the polypeptide returns to its original conformation. 20 21 Question 13 (4 points) 2 23 24 How is polarity established in a protein? a) proteins label the ends of their backbones with special chemicals 25 b) polarity is established by a phosphate group added to the end of a polypeptide chain. the amino group present on the first amino acid and the carboxyl group on the last amino acid, which are not involved in the formation of a peptide bond, establishes the polarity on the backbone. d) polarity is established because some side chains (on the first and last amino acid) of a seugence of amino acids are not involved in the formation of a peptide bond.