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Quiz 4 key (1) - Exposed hydrophobic peptides that are...

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Biochemistry 309, Winter 2010 20 points Quiz #4 NAME:_______________________________ TA:__________________ 1. What is the “melting point” for a double stranded DNA molecule. (2 points) The temperature at which half of the molecules are single stranded. 2. How is RNA chemically different from DNA? (2 points) RNA has a 2’OH on the ribose ring. How does this difference make RNA less chemically stable? (2 points) The 2’OH can attack the phosphate to hydrolyze the phosphodiester bond. 3. Cytosine can be methylated in DNA at the 5 position in the pyrimidine base. Does this affect its ability to basepair with guanosine? Explain. (3 points) No. This position is not involved in the basepair with guanosine. 4. What common structural feature of unfolded proteins is recognized during the heat shock response and the unfolded protein response? Why is this a good “marker” of misfolded proteins? (3 points)
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Unformatted text preview: Exposed hydrophobic peptides, that are usually buried in the core of proteins, are recognized during both heat shock and the unfolded protein response. 5. Give one reason why scrapies was thought not to be due to viral infection. (2 points) Because it was not sensitive to UV irradiation or ionizing radiation, which damage nucleic acids. 6. How does GroEL-GroES affect the energetic protein-folding funnel? (4 points) By smoothing the folding funnel in two ways. It prevents aggregation of folding intermediates, making dips in the funnel less deep. It also provides an optimal folding environment, decreasing energetic barriers, making hills smaller. What is the function of ATP hydrolysis in the GroEL-GroES cycle? (2 points) To recycle the chamber for folding of other proteins. Although binding to ATP allows the chamber to form, hydrolysis does not directly affect the rate of folding of the client protein....
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