question archive A)The quaternary structure of the native protein is held together by (a) only weak bonds (b) only covalent bonds (c) covalent and/or weak bonds -- can't tell from info given (d) both weak and covalent bonds
A)The quaternary structure of the native protein is held together by (a) only weak bonds (b) only covalent bonds (c) covalent and/or weak bonds -- can't tell from info given (d) both weak and covalent bonds
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A)The quaternary structure of the native protein is held together
by
(a) only weak bonds (b) only covalent bonds (c) covalent and/or weak bonds -- can't tell from info given (d) both weak and covalent bonds.
3B. Suppose you suspect that there is more than one type of subunit in the native molecule. So you treat the native molecule with mercaptoethanol and urea and try to separate the denatured protein into several components. If there really are 2 (or more) different types of subunits, which of the following methods is most likely to separate them?
(a) gel filtration (b) gel electrophoresis (c) paper chromatography (d) column chromatography based on solubility
For 3C-F. The native protein has 16 free SH groups per molecule. If you treat the native molecule with urea and mercaptoethanol, the 18,000 molecular weight component that you get has 6 free SH groups per 18,000. (Assume for this part that there is only 1 type of subunit in this protein.) If you treat the native molecule gently with mercaptoethanol alone, you do not change the molecular weight, but you get a protein with 32 free SH groups per molecule. Now if you add urea AFTER the gentle mercaptoethanol treatment, the molecular weight is reduced from 144,000 to 18,000. The 18,000 component obtained in this way has 4 free SH groups per molecule. Given all information so far, answer the following:
3C. How many subunits (polypeptide chains) are present in each native molecule? (a) 6 (b) 8 (c) 12 (d) 16 (e) >16.
3D. How many cysteine residues are present in each subunit? (a) 4 (b) 6 (c) 12 (d) 16 (e) 32.
3E. How many S-S bonds are present in each native molecule? (a) 4 (b) 7 (c) 8 (d) 16 (e) >16.
3F. How many S-S bonds are formed within each polypeptide chain (connecting different parts of the SAME chain)? (a) 1 (b) 2 (c) 3 (d) 4 (e) 6.
3G. Draw a picture of the protein that fits all the data. Be sure it shows all S-S bonds and all free SH groups in the native protein. Show or explain how your model fits all the experimental results.
