Feedback for Multiple Choice Quiz 9

  All of the correct answers have a green check mark.
  Incorrect answers have the "red-lit" button next to your choice.
  1. The best answer is a globular domain. A multimeric protein has two or more chains, however, they do not always have a tertiary structure, e.g tropomyosin, and other fibrous proteins.
  2. The metaphor refers to the hydrophobic core and the hydrophilic surface of globular proteins (and domains).
  3. The elements of secondary structure are usually much more rigid relative to the side chains on the surface of proteins.
  4. Aside from the absolute nature of the incorrect statements, note that when charged residues are found in the protien interior, they almost always have another residue of opposite charge nearby.
  5. Very few disulfide bonds ever exist for long in the reducing environment within cells. Disulfide bonds form outside the cell in contact with O2 and other oxidants.
  6. For a rough conceptual model, think of it this way: How many equally-sized balls can you pack around a central ball? Or better yet, look at the actual packing of hydrophobic side chains in a small protein such as protein G.
  7. It is the hydrophobic effect that drives these residues into the core due to the gain in entropy of the solvent when these residues lose their coat of ordered water molecules during the folding process.
  8. Although the hydropobic effect drives the non-polar residues into the core, the tight packing is due to van der Waals effects.
  9. Approximately 20kJ/mol is required to break an H-bond to water. Therefore if an H-bond is broken but not reformed, then the native structure will be destabilized by 20kJ/mol.