Which of the following statements best describes the hydrogen bonding

Question # 00680638 Posted By: dr.tony Updated on: 05/03/2018 01:53 PM Due on: 05/03/2018
Subject Biology Topic Biochemistry Tutorials:
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Which of the following statements best describes the hydrogen bonding network between deoxyhemoglobin (2HHB) and the Fe-heme ligand?




There are 2 direct hydrogen bonds between the ligand and hemoglobin amino acids.


There are no hydrogen bonds between the ligand and hemoglobin amino acids.


There are no direct hydrogen bonds between the ligand and hemoglobin amino acids, however there are 2 bridged hydrogen bonds that connect the Fe-heme to the protein via a water molecule.


There are no direct hydrogen bonds between the ligand and hemoglobin amino acids, however there are 2 bridged hydrogen bonds that connect the Fe-heme to the protein via atomic oxygen.




In both structures, the most abundant noncovalent interactions are the multiple hydrophobic interactions between the _______ of Fe-heme and the ______ in the binding site.




carbon groups; polar amino acids


carbon groups; nonpolar amino acids


iron atom; polar amino acids


iron atom; nonpolar amino acids




Which of the following statements is consistent with the interaction between His 92 of Chain B and the Fe-heme of deoxyhemoglobin?




His 92 donates electron density to the iron atom via the lone pair on atom NE2.


His 92 donates electron density to the iron atom via the lone pair on atom ND1.


His 92 forms an ion pair with the iron atom.


His 92 accepts electron density from the iron atom.




Which of the following statements is consistent with the binding of oxygen to hemoglobin (1HHO)?




Oxygen donates electron density to the iron atom and accepts electron density from the side chain of His 92?.


Oxygen accepts electron density from the iron atom and accepts electron density from the side chain of His 92?.


Oxygen donates electron density to the iron atom and donates electron density to the N—H group in the side chain of His 92?.


Oxygen accepts electron density from the iron atom and donates electron density to the N—H group in the side chain of His 92?.




In deoxyhemoglobin, which of the following subunit pairs has the longest distance between the iron atoms of the Fe-heme groups?




?1-?1


?1-b1


?1-?2


?1-?2




Upon oxygen binding, the distance between the iron atoms of the ?1 and ?1subunits _______.




decreases by 1.8 Å


increases by 1.8 Å


increases by 10.4 Å


remains the same




Upon oxygen binding, the distance between the NE2 atom of His 92 and atom C3A of the heme group in the ?1subunit _______.




decreases by 0.5 Å


increases by 0.5 Å




Upon oxygen binding, what is the fate of the ion pairs between (1) the C-terminal carboxylate of Arg 141 of the ?1chain and the side chain ammonium of Lys 127 of the ?2 chain and (2) the side chain of Arg 141 of the ?1 chain and the side chain of Asp 126 of the ?2 chain?




(1) broken; (2) remains intact


(1) remains intact; (2) broken


(1) broken; (2) broken


(1) remains intact; (2) remains intact




In deoxyhemoglobin, Tyr 42 from the ?1chain is hydrogen bonded to Asp 99 from the ___ chain, and upon oxygen binding, this interaction is disrupted due to ___________.




?2chain; rotation of only the side chain


?1chain; rotation of only the side chain


?1chain; significant movement of the backbone


?2chain; significant movement of the backbone





Which of the following observations supports the conclusion that oxygen binding causes a conformational change in hemoglobin?




The hydrogen bond between Tyr 42 from the ?1chain and Asp 99 from the ?2chain is disrupted.


The distance between the iron atoms of the ?1 and ?1subunits changes.


Each of these observations supports the conclusion.


The interaction between Arg 141 of the ?1chain and the side chain of Asp 126 of the ?2 chain changes.

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