AAMC C/P Section Bank

[sapientnarwhal]

So I just started the C/P section bank with the intent of doing 59 questions in 95 min. After the first 17-18 questions I found that I have a strong grasp of the concepts and principles to solve each problem, but I am missing a couple questions involving the small memorization details (e.g. knowing that a voltmeter measures 0 when the potential difference between two circuit elements in parallel are identical. I looked this up and was promptly able to solve the problem. though had I not known this I would have been screwed).

Basically I am confident that I could score >80-85% correct by skipping difficult problems here and there, but given that I just scored a 131 on C/P for AAMC FL1 (the 3 that I missed were stupid mistakes too) I feel as if I could do better. This section bank seems far more difficult than AAMC FL1.

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[westsidestoryz]

so...was this a question or a statement?

 

[OchemOficionado]

Cool.

It’s likely that the real thing will be more like the S/B. Do FL 2 and 3 before you get too excited.

 

[917137]

The section bank is not always an accurate depiction of what the real test will look like. The FL's are a far better indicator content wise, but they're still not perfect. The FL predicted my score pretty well and I've heard the same from other people besides a 1-2 point variation. I would recommend spending more time practicing passages from other sources because some of the memorization/recall questions in the section bank are a lot less likely to show up on your test.

 

[alyxxs]

Can someone help me out with Question # 36? This whole passage was confusing but that questions especially. I tried to link a

 

[sapientnarwhal]

Can someone help me out with Question # 36? This whole passage was confusing but that questions especially. I tried to link a View attachment 233386 View attachment 233387 View attachment 233388

Based on the structure of the bimetallic center and the mech description, we can infer that the AA residues stabilize the Zn centers, which then interact with an H2O necessary for the initiation of catalysis. Replacing these polar AA with alanine, a nonpolar aliphatic AA, reduces the interactions with the bimetallic center (residues 80, 148, 113, 175, 373), which in turn disrupts interactions with water (also residue 147 no longer deprotonates the H2O bound by the active site involved in amide hydrolysis). Therefore the answer is D.

C is incorrect because introducing hydrophobic active site residues would actually destabilize the active site (this should be obvious given the frequency of hydrophilic/charged/polar AA and the relevance of H2O in the active site). This is evident in the reduced melting temps in the variants. In my experience, MCAT passages rarely introduce results that contradict the initial hypothesis. Results will likely corroborate or partially support the hypothesis.

THOUGHT PROCESS: they are substituting polar AA with nonpolar AA. Probably going to screw up those interactions depicted in Figure 1 and the mech. Table shows each variant results in low substrate affinity and enzyme instability.
for A, coordinate bonds do not change the net charge of the metallic center.

 

[alyxxs]

Based on the structure of the bimetallic center and the mech description, we can infer that the AA residues stabilize the Zn centers, which then interact with an H2O necessary for the initiation of catalysis. Replacing these polar AA with alanine, a nonpolar aliphatic AA, reduces the interactions with the bimetallic center (residues 80, 148, 113, 175, 373), which in turn disrupts interactions with water (also residue 147 no longer deprotonates the H2O bound by the active site involved in amide hydrolysis). Therefore the answer is D.

C is incorrect because introducing hydrophobic active site residues would actually destabilize the active site (this should be obvious given the frequency of hydrophilic/charged/polar AA and the relevance of H2O in the active site). This is evident in the reduced melting temps in the variants. In my experience, MCAT passages rarely introduce results that contradict the initial hypothesis. Results will likely corroborate or partially support the hypothesis.

THOUGHT PROCESS: they are substituting polar AA with nonpolar AA. Probably going to screw up those interactions depicted in Figure 1 and the mech. Table shows each variant results in low substrate affinity and enzyme instability.
for A, coordinate bonds do not change the net charge of the metallic center.

Thanks! I think I was initially confused because I wasn't thinking of the residues as Amino acids.