George wants to increase his consumption of provitamin A for the possible cancer risk-reducing effects. Which of the following foods should he choose?

Pellagra is characterized by all the following except

Is the bolded statement TRUE or FALSE? Changes in bond enthalpy are calculated by taking the difference between the enthalpy of the bonds broken and the enthalpy of the bonds formed (dH = Hbonds broken – Hbonds formed).  Given this changes in bond enthalpy: 16. are always negative for a reaction in which more bonds are formed than broken. 17. when positive, indicate the formation of bonds. 18. when negative, will destabilize a system (such as a protein), and are therefore considered thermodynamically unfavorable. 19. are always positive for an endergonic process. 20. would be negative if hydrogen bonds were being broken in order to form covalent bonds.

Which of the following is true about the forms of vitamin A?

Is the bolded statement TRUE or FALSE? Two biomolecules are known to interact with one another in order to facilitate a biological process.  One of these molecules is a protein the other is a small molecule found in the cell.  Given this classify the following statements as true or false.   56. If mutation of a glutamate to a leucine in the protein negatively impacts the binding, it is reasonable to say that ionic bonding facilitates binding between the two biomolecules. 57. Formation of hydrogen bonds between the two biomolecules is enthalpically favorable and will contribute to the strength of interaction between the two. 58. Hydrophobic interactions are incapable of stabilizing (making favorable) the interactions between the two biomolecules. 59. An ionic bond between the two biomolecules would be stronger if it formed in a hydrophobic pocket on the surface of the protein relative to a hydrophilic pocket. 60. Free energy will remain unchanged when comparing a state in which the biomolecules are not interacting and a state when they have formed the interaction.  

Is the bolded statement TRUE or FALSE? The predominant form of Glu at a pH of 3.0: 31. has a protonated side chain which has a neutral charge. 32. has a net +1 charge. 33. has a side chain capable of forming an ionic bond with the side chain of His at the same pH. 34. is classified as an acidic side chain. 35. will have a -1 charge when found in the middle of a peptide

Is the bolded statement TRUE or FALSE?   In class we spent a significant amount of time discussing the structural features of the peptide backbone.  Given this which of the following statement(s) is (are) true? 41. All conformations of the backbone are energetically equivalent. 42. Each amino acid can have at least two dihederal angles that, when changed, result in a new conformation for the peptide backbone. 43. Some phi/psi angles are not favored because they cause steric clashes in the backbone. 44. The cis configuration for the peptide bond, if adopted in the absence of a proline, will destablize the protein. 45. Formation of an alpha-helix requires backbone hydrogen bonding but NOT specific phi/psi angles adoption.

Short answer Instructions-   On this exam you must answer a single free response question.  The question is worth 10  points, be as concise as possible.     Stated below is the primary structure of a small peptide that is known to form an α-helix.  Using this sequence answer the following questions:   +H3N-RKMVDILKR-COO-   How many peptide bonds exist in this protein (1 point)? ___________ What would the charge of this α-helix be at pH 8.5 (assume pK’s remain constant)? (2 points) ___________ Using the diagram below, would you say that this helix is amphipathic? If your answer is yes, state the number (residue #1 or #2 for example) of the residues that are hydrophilic (assume R represents residue #1 in the diagram)? (3 points) ___________ Finally, if I were to replace the 5th amino acid with a K side chain would this have any effect on the formation of the helix at pH of 13? How about pH of 7? Why do you think so for both pH’s? (4 points)

Is the bolded statement TRUE or FALSE? Tertiary and quaternary structures are the final levels of protein structural hierarchy.  51. Subunits are held together by non-covalent forces to make up the quaternary structure of a protein. 52. The hydrophobic core of a globular protein forms when two subunits with hydrophobic interfaces come together. 53. Non-covalent interactions between amino acids side chains within a single tertiary structure only form between amino acids close to each other in the primary structure. 54. Quaternary structures can consist of no more than 7-subunits.55. The quaternary structure of a protein can be formed by subunits of identical primary structure or differing primary structures.

Is the bolded statement TRUE or FALSE? Hydrogen bond(s): 26. only form in polar solvents. 27. are interactions between dipoles that are formed (the dipoles) when atoms of differing electronegativity form covalent bonds. 28. formation is not important in protein folding as large numbers of hydrogen bonds must also be broken between the unfolded protein and the solvent. 29. when forming, can contribute to a negative change in enthalpy. 30. when forming, can contribute to a negative change in free energy.