AAMC CBT10 only OFFICIAL Q&A

[Vihsadas]

This is the official Q&A thread for AAMC CBT10.

Please post ONLY questions pertaining to AAMC CBT10.
Out of respect for people who may not have completed the other exams, do not post questions or material from any other AAMC exam.

Please see this thread for the rules of order before you post.

Good luck on your MCAT!

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[MichaelRowle]

Having trouble visualizing this.

 

[Chemist0157]

Image a colored drop on a surface of water. The colored drop is oleic acid, which just so happens stands straight up in pure water but lays side-by-side in an acidic solution. At the moment, the colored drop represents oleic acid molecules standing up straight. Adding HCl acidifies the solution so the oleic acid molecules lay down. They are now more spread out; that's why we would expect the diameter of the monolayer (colored drop) to increase in HCl.

 

[SuperOrchestra]

137 bio.

The wording of this question threw me off, it says the addition of an adrenergenic drug brings the membrane potential from -60 to -70, making me feel that the drug is doing the work, so it must be acting on the sodium because the sodium pump is active.
Now if the question was, how does a cell go from a membrane potential of -60 to -70, I would have said the potassium channels because they are of important in that final stage of repolarization as it flows down its concentration gradient outside the neuron.

Was this question more straight forward to you guys? Am I missing something?

 

[unsung]

137 bio.

The wording of this question threw me off, it says the addition of an adrenergenic drug brings the membrane potential from -60 to -70, making me feel that the drug is doing the work, so it must be acting on the sodium because the sodium pump is active.
Now if the question was, how does a cell go from a membrane potential of -60 to -70, I would have said the potassium channels because they are of important in that final stage of repolarization as it flows down its concentration gradient outside the neuron.

Was this question more straight forward to you guys? Am I missing something?

Yeah, I see what you're saying. But basically I think all they wanted us to do is associate repolarization with K and depolarization with Na. It's not clear how a drug would act on Na channels to effect repolarization.

Just think: depolarization = sodium influx, and repolarization = K efflux. I think that's the main point of what they want us to know. So if you look at it that way, going from -60 to -70 is repolarization so it has to have something to do with the K voltage-gated channels.

 

[AZFutureDoc]

My verbal tutor from Princeton Review with a PhD from Harvard agrees. He doesn't think any answers are good, and A isn't even the best answer he said. He consistently can score 15 on VR using 45 minutes too lol. It's incredible.


EDIT by Vihsadas: This post was originally in response to this thread:
http://forums.studentdoctor.net/showthread.php?t=411676
In line with the Rules of Order posted at the top of the study Question Q&A, I have moved all posts subsequent to this one from that thread into the official AAMCCBT10 thread. The reason for this move is so that future test takers who have not taken CBT10 don't accidentally see anything about the exam before they have used it for practice. Thanks, and good luck on your MCAT!

 

[cornpops21]

If you look at the answer explanation for A, it actually confirms that A is the right answer. It was a mistake on their part. You got the question right.

 

[willis06]

I missed the same thing. absurd.

Did anyone get this question right?

 

[ziggydoc]

I thought they made a mistake too, and I was 1 question away from a 12 on that section, so I guess I'll just call it a 12 then Since that will make me feel better about my real deal which I took 3 days after AAMC 10 (33 total on AAMC 10)

 

[starl3tte]

Would anyone be willing to sell me a .pdf of AAMC #10 + solutions at a reasonable price? I've been looking around, but time is tickin'.

 

[Gear2d]

I way confused about this problem (number 26 in Passage IV). I thought an indicator is selected based on pH = pKa +/- 1. Based on this formula shouldn't the answer be "C". Because Titration 1 has a pKa of less than 2, and Titration 4 a pKa of about 5 (Got the pKa from the half-equivalence point). Can someone please tell me what I am doing wrong.

Do I use the equivalence point here instead, where Titration 1 is at 7, and Titration 4 is a little bit above 7 (maybe 8 or so), and the only one that covers those pHs is Indicator E? If that is case when do I use that formula about then?


Thank You in advance for any help

 

[Chemist0157]

All you need to pay attention to are the equivalence points of Titrations 1 & 4. Titration 1 appears to be about 8, and Titration 4 seems to be about 9. So indicator E is the best choice since its range is 8-10.

 

[pitt1166]

Hey, I'm really hoping someone can help me with my Q, as I take the test in two days (argh!).

OK, #135. The question asks about what factor would have an affect on the release of norepinephrine into the nerve terminal-receptor junction.

The answer is that changing the extracellular concentration of Calcium ions would have the greatest affect.

The explanation says that "When an action potential reaches a nerve terminal it triggers the opening of calcium ion channels in the neuronal membrance. Because the extracellular concentration of calcium ions is greater than the intracellular concentration, calcium flows into the nerve terminal. This triggers a series of events that cause the vesciles containing norepinephrine to fuse with the plasma membrane and release NE into the synapse."

OK, so I'm a bit confused, kind of shocked actually. I must have missed studying the part where it talks about this stuff. I mean, I know about calcium release triggering and muscle contraction, no problem there.

But what is this about calcium flowing out of the cell into the synapse and thereby causing NE to be released? I totally must have missed that. Is the calcium ion some sort of critical signalling molecule in the sympathetic nervous system? Please someone, for the love of god, explain.

But seriously, any help would be thoroughly appreciated. Even direct me towards what I'm missing.

 

[Tiss229]

It's a subtle point and you probably glossed over it while studying. When an action potential reaches the end of the presynaptic neuron, Ca2+ voltage gated channels open causing calcium to flow into the cell. The influx of calcium causes the neurotransmitters to be released into the synapse.

Breath bro, itll all work out great

 

[pitt1166]

It's a subtle point and you probably glossed over it while studying. When an action potential reaches the end of the presynaptic neuron, Ca2+ voltage gated channels open causing calcium to flow into the cell. The influx of calcium causes the neurotransmitters to be released into the synapse.

Breath bro, itll all work out great

Subtle point indeed. That does seem to make sense though. If I could trouble you on one further point, kind sir...

So extracellular calcium ion concentrations in the synpatic gap are high, relative to intracellular concentrations in neurons. At the same time, calcium ions are stored in the SR of muscle cells. These two situations are separate phenomena, correct? I mean, obviously they are inherently related as any two things in our body are, but in order to understand them, I should few them as two separate processes that both happen to use calcium?

And just one other thing... this calcium inflow/NE outflow... this typically applies to neurotransmitters in general, correct?

 

[Tiss229]

Yes you should conceptually view them as separate. I recall reading somewhere that the process of Ca inflow--> neurotransmitter release is still not very well understood. As for the second point, yes as far as I understand it that is the mechanism for neurotransmitter release.

 

[farf]

Yeah I think the Ca comes in through the same slow-gated voltage channels that are used in the heart nodes to prolong the contractions, and the same channels are used in the neuron and in the muscle fibers. And yes, it's not understood how the Ca influx causes neurotransmitter release.

 

[kuriosity]

Can someone send me the answers to this exam? I saved it on my computer but I think I might've deleted the answer PDF by mistake. :[

 

[engineeredout]

OK, I just finished the AAMC 10 and there was a question on the Bio section about "voles." I was like, WTF, what is that?? (They are mice-related.) Is there a lot of random crap knowledge like this on the real MCAT? I feel I am at a particular disadvantage because English is not my native language.

Oh, and "voles" were not defined in the passage nor was there anything in the passage that could allow you to infer what it was.

I know this is an older post but I just wanted to toss in that I picked mice because I guess that it didn't originate from humans, and that the mice being mammals were closer to humans than the other choices so wouldn't it be most likely that the disease eminated from them?


Got 12PS/11VR/10BS. Same exact score as #9. I know a lot of people complained about the difficulty of the VR but I really didn't think it was that different than 9 or 8 or any of the others for that matter. So frustrating that 48/52 correct is only a 12 though for PS. 4 questions = 3 points GAH.

#137 (BS): If a cell membrane's potential changes from -60mV to -70mV after treatment, the NE receptor is most likely linked to:

C: A sodium Channel
D: A potassium channel

D is the answer but why couldn't it be C?


#123: It is now generally accepted that H. Pylori can cause ulcers. Proof of this is most likely dependant on the demonstration that...

A. Ulcers can be produced in healthy individuals by infecting them with H. Pylori.


Don't you ever run into one of these bio experiments on the mcat where the answer has to do with the fact that the answer choice is unethical? I mean who the **** would volunteer to be purposely infected and develop an ulcer?



#54: 2nd question on VR: Somebody said before that the answer choice B is a mistake and the actual answer is A. Is this correct? Doesn't make too much of a difference to me as my VR grade will stay the same. I was just curious.


#20: What is the magnitude of the detected frequency shift during the projectile flight in the passage (goes up and comes to a stop at max height h)

A. It falls linerally to zero, then increases.


How the **** does the magnitude begin to increase again? I'm really having trouble with this question. Can someone explain it?


#26: Why does indicator F with a pH range of 10-12 not work?


I think thats it. I know thats a lot but even though I didn't think the test was bad it just seems like the questions I did get wrong are really wtf.


And did anyone else hate that particle accelerator passage or was that just me?

 

[baller99]

I know this is an older post but I just wanted to toss in that I picked mice because I guess that it didn't originate from humans, and that the mice being mammals were closer to humans than the other choices so wouldn't it be most likely that the disease eminated from them?


Got 12PS/11VR/10BS. Same exact score as #9. I know a lot of people complained about the difficulty of the VR but I really didn't think it was that different than 9 or 8 or any of the others for that matter. So frustrating that 48/52 correct is only a 12 though for PS. 4 questions = 3 points GAH.

#137 (BS): If a cell membrane's potential changes from -60mV to -70mV after treatment, the NE receptor is most likely linked to:

C: A sodium Channel
D: A potassium channel

D is the answer but why couldn't it be C?


#123: It is now generally accepted that H. Pylori can cause ulcers. Proof of this is most likely dependant on the demonstration that...

A. Ulcers can be produced in healthy individuals by infecting them with H. Pylori.


Don't you ever run into one of these bio experiments on the mcat where the answer has to do with the fact that the answer choice is unethical? I mean who the **** would volunteer to be purposely infected and develop an ulcer?



#54: 2nd question on VR: Somebody said before that the answer choice B is a mistake and the actual answer is A. Is this correct? Doesn't make too much of a difference to me as my VR grade will stay the same. I was just curious.

137 - the only way (for the mcat atleast) to decrease membrane potential is either to let out potassium. sodium channels will let in sodium (electrochemical gradient) making it more positive.

123 - i totallly agree with you. mcat is real dumb sometimes...i just don't know when to be realistic. i'm kinda scared that the ppl who wrote that question might be actual doctors.

54 - yeah thats wrong. aamc messed up

 

[engineeredout]

137 - the only way (for the mcat atleast) to decrease membrane potential is either to let out potassium. sodium channels will let in sodium (electrochemical gradient) making it more positive.

Gah. Stupid mistake but thats going on my list of quick facts. Thanks.

Brings up something though. I know that with the potassium leaving it makes the voltage difference more negative, but that doesn't mean that there is an increased membrane potential? When saying increased/decreased that doesn't refer to the magnitude of the membrane potential? I mean if you have a membrane potential of 0, thats still a higher potential than -70, but nothing will happen.

 

[baller99]

Gah. Stupid mistake but thats going on my list of quick facts. Thanks.

Brings up something though. I know that with the potassium leaving it makes the voltage difference more negative, but that doesn't mean that there is an increased membrane potential? When saying increased/decreased that doesn't refer to the magnitude of the membrane potential? I mean if you have a membrane potential of 0, thats still a higher potential than -70, but nothing will happen.

well i think that you can treat voltage difference as equal to potential. so if there's increased potential, then the potential is higher. but 0 is worse than -70 since ions will have a potential to flow into the cell. For +70 ions will have a potential to flow out of the cell. the magnitude really determines how "strong" the potential is, while the sign just tells you the direction.

 

[Ninjaface]

For that DDT, H+ question I got it by just thinking the effect was analogous to the effect mentioned about Na+ - increased membrane permeability to a small, positive ion.

I got the liver failure question wrong though, as i thought that the liver produced albumin, the primary blood plasma protein, and that this would have a huge effect on osmotic pressure and thus blood pressure.

No?

edit: Also, as the neuronal membrane is more permeable to k+ than sodium, it's concentration is the determining factor in the resting potential. I knew that because I have a MSc. in neuroscience though, which is kind of like cheating.

edit3; Question 98: The passage itself says DDT interferes with cell division, so I put mitosis, but instead the answer was something about calcium, which was never mentioned in the passage. Bah. I guess I was applying a VR strategy to answer this one and it didn't work out.

edit2: Also, really strange, and I assume unique to me and my safari browser as no-one else has mentioned it, but 3 completely random questions in the CBT had the answer explanation given, during the practice. Just 3. I think I would have gotten them right anyways, but still, WTF?

 

[gadabout]

can anyone help with #141? why 1-floro-1-methylcyclohexane and not 2-floro-1-methylcyclohexane? i think i have an idea why but the solution doesn't go into detail about this.

 

[engineeredout]

I got the liver failure question wrong though, as i thought that the liver produced albumin, the primary blood plasma protein, and that this would have a huge effect on osmotic pressure and thus blood pressure.

It wasn't a good question, but the way I saw it, A and B said the same exact thing, and C is the primary function of the liver, leaving only D as an answer choice.

 

[not respect]

ok for the doppler one, it starts increasing again because its relative velocity to the medium increases.

123, is one of koch's postulates

 

[Ninjaface]

It wasn't a good question, but the way I saw it, A and B said the same exact thing, and C is the primary function of the liver, leaving only D as an answer choice.

Yeah, you're right, but the fact two of them said pretty much the same thing made me think one of them wasn't the answer. Over-strategizing again, one of my biggest probs. I have yet to get one of the "hard" physics problems wrong yet, but consistently get only around 80 % of the easy ones. Looking for too many tricks...

 

[futuredoctor10]

#123: It is now generally accepted that H. Pylori can cause ulcers. Proof of this is most likely dependant on the demonstration that...
C. Ulcers can be produced in healthy individuals by infecting them with H. Pylori.

Don't you ever run into one of these bio experiments on the mcat where the answer has to do with the fact that the answer choice is unethical? I mean who the **** would volunteer to be purposely infected and develop an ulcer?

Yeah I thought the exact same thing! I think I spent, literally 4-5 minutes on this question. I thought, C cannot be correct because you would never infect healthy individuals with ulcers. But then I found problems with other answer choices and ultimately picked C.

Although I am curious how we are supposed to know on the real thing when to make such assumptions (you'd never infect humans for an experiment)? I can just picture the explanation to this question, where it could have said: "You would never realistically demonstrate proof by intentionally infecting humans, so C is not the correct answer"

And did anyone else hate that particle accelerator passage or was that just me?

Yes I didn't like that passage! I only missed one but was unsure of probably 1/2. I don't know it is really hard to distinguish answer choices for those questions- I was not sure what I could assume or not assume and the passage didn't really help too much for some questions. Anyone feel the same way? Any techniques on how to tackle such a passage on the real thing?

 

[T12]

in kaplan's explanations for this question they list the correct answer as the one we all picked. sorry to resurrect this thread but I saw it initially at a time when I was temporarily banned and forgot until now, thought I'd throw that out there!

 

[engineeredout]

Definitely a mistake. Unfortionately it didn't affect my VR score on this exam (Already an 11)

What kind of a world do we live in in which 36/40 = 90% doesn't warrent higher than 11 (11/15 = 73%) BAH.

 

[JasonE]

The Kaplan explanations also think that A is a better answer for 54.

also,
i had a problem with #57. the passage says that Dort has not drilled yet but will this summer. the question prompt says that dort has not found a crater or bedrock yet. id think the answer would be B (the info in the question prompt is irrelevant) because dort already knows he hasn't found evidence yet and that he needs to. whats the point of some scientist telling him something he already knows he hasnt but will do?


I think the AAMC should let you review your actual mcat to make sure all their answers are correct becuase they are CLEARLY wrong here, but they would never do that because it would create too much controversy and work for them (god forbid).

 

[BlueElmo]

32 composite for me. I also got that question wrong. so the consensus is that AAMC is the wrong one? Urg, I'm still looking at a 33/40, then, which is still a 10. Such a bull, how can missing only 7 mean still a 10?

 

[mosquitoman]

did you guys have a problem with questions #123 and #127 ?

For 123 i had it narrowed down between a and c.. how can they say proof depended on ulcers being produced in healthy people? I mean hey.. that is concrete proof.. but that is a messed up way of harming another individual! same for 127
let's inject someone healthy and see if they possible develop an ulcer

great idea AAMC.. really living up to hipocratic oath!

 

[aishlover]

I had a question from AAMC 10 VR. The second question of the first passage (Item 54) says "Dort mentions sinkholes in order:" and then there are the choices. I picked A, which said, "to eliminate an alternative hypo. regarding the formation of the crater." It is the wrong choice, but I don't understand the explanation as to why it is wrong. The explanation says "The elimination of an alt. hypo. is the reason for the reference to the sinkholes, with the explanation that 'the rock formations aren't the sort to collapse and form sinkholes.'"
Can someone please tell me what is it that I am not getting here?
Thanks

 

[mosquitoman]

yea it was discussed before.. their answer key is wrong

you had the right one

 

[aishlover]

yea it was discussed before.. their answer key is wrong

you had the right one

oh it was discussed before? I didn't know about it. Great, so I was right.
Thanks a lot mosquitoman!

 

[Vihsadas]

Moving to the official thread.

 

[Lukkie]

so 54 really is A? i mean i'm reading the answer, and their explanations and they are all pretty bad.

the curve on this exam overall is insane. i missed 4 on VR and it knocked me down to 11! discounting #54, getting 37/40 is only a 12! ouch!

the vole thing was pretty stupid too. i guess i got lucky on that one

 

[Lukkie]

How about those poor people who got 36 for a 11? haha

so missing 4 is an 11, and missing 7 is a 10? WTF curve is this?

im really hope they messed up the curve calculation, just like they messed up the sinkhole answer

i mean the answer they selected was hilarious. "the author wanted to impress his friends with this knowledge" or something

 

[Ari1584]

For BS, passage 3 on the pulmonary function/hantavirus graph....

113) I had no idea on how to get the answer to this question. The main thing i was confused on is..i thought antibodies are NOT made for viruses?? I thought that only T-cells help to destroy viruses and antibodies are only made for bacteria?? And also, i thought the actual virus they found WAS the hantavirus, not that it was related to it and thats why i didnt pick the correct answer, which was B. I definitely need some explaining on this one!!

115) It said why did investigators conclude that the new pathogen is the hantavirus?...I picked answer B- it showed the virus infected the lungs. My reasoning was that from the hybridizing and growing the virus in bacteria and injecteing the antibodies, etc...that proved that the hantavirus was the one that caused the disease since the antibodies were found in the lung epithelium. Why is that a WORSE answer than A?

Passage 6- adrenergic drugs

134) I thought then when you inhibit enzymes which degrade Neurotransmitters in the synapse, there is a build up of that transmitter which ultimately leads to decreased function...that is why i picked B. But the answer is A, the opposite of what i picked. I could have sworn i had similar questions to this before and the answer was decreased activity. What am i missing here?

 

[onb2014]

131. Could someone explain why the amide could not also be correct in addition to the anhydride? Also, how does the acid chloride even work with an acetylation reaction?

 

[banister]

If you look at reactivity charts, you will see that for the carboxylic acid derivatives, that Acetyl Chloride is the most reactive, followed by anhydrides > esters >> amides. This has to do with how the "leaving group" is. When an alcohol adds to the carbonyl carbon, it eventually kicks out what was on it, and how reactive it is depends on how well the leaving group can stabilize the negative charge. Cl- is the best because it is electronegative and can stabilize the charge well. The resulting carboxylic acid from anhydride can stabilize it well because of resonance from the carbonyl. Amides are terrible at it because it does not want the negative charge on it. Sorry, I'm kinda rushed, but hope this makes sense.

131. Could someone explain why the amide could not also be correct in addition to the anhydride? Also, how does the acid chloride even work with an acetylation reaction?

 

[FutureScaresMe]

Item.88
According to the passage, the demonstration that an unknown object closer in size to a prototypical quarter than to a prototypical pizza was called a pizza challenges the prototype model by suggesting that the judgment was an inductive inference. The most reasonable objection to this conclusion would be that:

A. the author offers no other evidence to support it.
B. the judgment indicates a lack of knowledge about the concepts.
C. the construction of a prototype is also an inductive process.
D. the diameter of flattened quarters can be unusually large.

If the construction of a prototype is also an inductive process, wouldn't that be support for the conclusion that judgments are based on inductive inferences, and not object to it?

 

[isaacmn]

can some help me with #14? Why does K violently react with cold water oppose to Mg, Zn...?

This goes back to the solubility rules, all group 1 are soluble which include ammonium salt as well. Being that K+ is in group 1, it is very soluble. Take a penny and put it in a cold water, does it dissolve?????. Put a Nacl or KCL( they have the same properties because they are in the same group ) in water, it dissolves rapidly.

 

[isaacmn]

For BS, passage 3 on the pulmonary function/hantavirus graph....

113) I had no idea on how to get the answer to this question. The main thing i was confused on is..i thought antibodies are NOT made for viruses?? I thought that only T-cells help to destroy viruses and antibodies are only made for bacteria?? And also, i thought the actual virus they found WAS the hantavirus, not that it was related to it and thats why i didnt pick the correct answer, which was B. I definitely need some explaining on this one!!

115) It said why did investigators conclude that the new pathogen is the hantavirus?...I picked answer B- it showed the virus infected the lungs. My reasoning was that from the hybridizing and growing the virus in bacteria and injecteing the antibodies, etc...that proved that the hantavirus was the one that caused the disease since the antibodies were found in the lung epithelium. Why is that a WORSE answer than A?

Passage 6- adrenergic drugs

134) I thought then when you inhibit enzymes which degrade Neurotransmitters in the synapse, there is a build up of that transmitter which ultimately leads to decreased function...that is why i picked B. But the answer is A, the opposite of what i picked. I could have sworn i had similar questions to this before and the answer was decreased activity. What am i missing here?

In regards to number 113, this is an example when the mcat does not require ur outside knowledge or memorization to answer the question. The point here is that antibodies in the body produce protein that are specific to the antigen or foreign protein or antigenically related to the foreign protein. IF infected with lets say A strain of hantavirrus, remeber you can still be suceptible to a different strain of hantavirus infection because your body only produces the A strain hantavirus anibodies and nothing more. They dont know its hantavirus yet according to the passage so you are using a knowledge outside of the passage. Stay away, I know its hard to.

 

[isaacmn]

can anyone help with #141? why 1-floro-1-methylcyclohexane and not 2-floro-1-methylcyclohexane? i think i have an idea why but the solution doesn't go into detail about this.

It deals with the leaving group, fluorine is a bad leaving group so it will form the least stable state which eliminates chlorine being a better leaving group. You are down with 1-floro and 2-floro, if dehydration occurs in 2- floro it will most likely result in trisubstituted because of the methyl group. But since the methyl is on the same carbon with floro in 1 floro, then it will result in the disubstituted being asked for.

 

[TooMuchResearch]

did you guys have a problem with questions #123 and #127 ?

For 123 i had it narrowed down between a and c.. how can they say proof depended on ulcers being produced in healthy people? I mean hey.. that is concrete proof.. but that is a messed up way of harming another individual! same for 127
let's inject someone healthy and see if they possible develop an ulcer

great idea AAMC.. really living up to hipocratic oath!

One of the principle H. pylori researchers actually drank a culture of the bacteria to induce an ulcer. It was treated with antibiotics. This is how it actually happened...you can find a better source, but here is a start: a Wikipedia page.

 

[junkct]

I had a lot of problems with the BS. I mean usually when I get a question wrong on a science section, I look at the correct answer/explanation and go "OOOH okay, that makes sense". This time there were a good number of questions where I didn't have that reaction. I think this BS section just sucks in general; I feel like a lot of the correct answers were (very) arguable...

but first of all, I actually thought the vole question wasn't all that tricky. it was very deducible from the passage. the passage said the virus was found in rural communities (reasonably eliminating humans/fish), and just the fact that all the patients walked in not knowing what the heck caused their disease is what made me pick "mouse" as the answer. I mean seriously, if I were bitten by a snake and then developed a disease shortly thereafter, I think I'd probably link it back to the snake. Maybe I just had fluky logic? LOL



But now onto the ones I'm mad about:

#98: Ca2+ deposition the eggshell? All the passage says is that the shell is brittle. Doesn't the amniotic membrane make the shell as well? And didn't the passage say something about DDT screwing with estrogen? and isn't estrogen closely linked with amniotic membrane formation? that's why i put amniotic membrane as the answer

#101: Fractional distillation?? What about recrystallization?? I understand that they have diff boiling points, but they also have diff melting points (in which case recrystallization would work). I narrowed it down to these two answers, and picked recrystallization because it said that one of the molecules was moderately flammable, so I thought that if you attempted fractional distillation, it might ignite. Therefore, recrystallization is more practical. What am I missing about recrystallization here?

#123: WTF. unethical much? seriously. I picked A (ppl with ulcers have H.Pylori antibodies). I know that correlation doesn't imply causation and all that junk, but seriously, there have been numerous questions on the mcat where there are two feasible answers and where the mcat chooses one as the correct answer because the other answer is "impractical or inefficient or expensive". I figured this would be one of them. and I don't care if one of the principal researchers on this topic drank an H.Pylori culture and developed an ulcer. That's no more proof than answer choice A. One experiment (and for you research nerds, a sample size of n=1) does NOT suffice to make a conclusion like that. And I'm 99% certain that these researchers would be unable to find more than 3 people to volunteer for an experiment like this. So on the basis of that, Answer choice C should be elminated because it is impossible to perform a reliable study of that sort.

#127: Ok i'm going to try my best to explain this. I picked choice A because urease is an enzyme (a protein), which is produced by the strain. So if you expose an ulcer patient to urease antibodies and the ulcer goes away, wouldn't this imply that H.Pylori requires urease for colonization? I had problems with choice B because the passage says that H.Pylori PRODUCES urease. Therefore, if you expose uninfected individuals to H.Pylori without urease, this doesn't mean that the the H.Pylori can't just synthesize the urease on its own. Now if the answer choice had said "exposing uninfected individuals to H.Pylori without the urease GENE," I would've been sold, because now this means that the H.Pylori cannot produce the urease.

#129: Really?? Since when does a Grignard reagent attack an alcohol?? I'm not talking about the alcohol that was formed from the carboxylic acid... that makes sense. I'm talking about that other alcohol on the left of the molecule. How the heck would the grignard reagent add to that?!?



Yeah ok I'm sure I missed some stuff in there. I'm sure I'm wrong and AAMC is right (except for 123, wtf), but I'd really like to know what's wrong wtih my logic here. This test just kind of bugged me in general because I'm not used to seeing so many ambiguous choices. Every test I've taken before this was really straightforward, but if this test is most representative of the real thing, then I'm a bit scared (especially with VR, got a 33/40 and a 10? BS!)

/end vent

 

[TooMuchResearch]

#123: WTF. unethical much? seriously. I picked A (ppl with ulcers have H.Pylori antibodies). I know that correlation doesn't imply causation and all that junk, but seriously, there have been numerous questions on the mcat where there are two feasible answers and where the mcat chooses one as the correct answer because the other answer is "impractical or inefficient or expensive". I figured this would be one of them. and I don't care if one of the principal researchers on this topic drank an H.Pylori culture and developed an ulcer. That's no more proof than answer choice A. One experiment (and for you research nerds, a sample size of n=1) does NOT suffice to make a conclusion like that. And I'm 99% certain that these researchers would be unable to find more than 3 people to volunteer for an experiment like this. So on the basis of that, Answer choice C should be elminated because it is impossible to perform a reliable study of that sort.

The passage only says that H. pylori were isolated from 95% of patients with ulcers. It does not specify whether 95% of people without ulcers also carry the bacteria, so we really don't know if the bacteria cause the disease. For that reason, answer choice (A), "people with stomach ulcers to H. pylori," is not a correct answer. Answer choice (C), while difficult to perform and perhaps unethical, creates a causal link between the bacteria and stomach ulcers just as feeding high doses of aspartame to mice daily and finding elevated numbers of tumors within them after death creates a causal link.

It's not an ethics test, so the correct answer need not be the most ethical choice. Besides, answer choice (C) states that "ulcers can be produced in healthy individuals," and it does not specify that those individuals are human.

 

[junkct]

The passage only says that H. pylori were isolated from 95% of patients with ulcers. It does not specify whether 95% of people without ulcers also carry the bacteria, so we really don't know if the bacteria cause the disease. For that reason, answer choice (A), "people with stomach ulcers to H. pylori," is not a correct answer. Answer choice (C), while difficult to perform and perhaps unethical, creates a causal link between the bacteria and stomach ulcers just as feeding high doses of aspartame to mice daily and finding elevated numbers of tumors within them after death creates a causal link.

It's not an ethics test, so the correct answer need not be the most ethical choice. Besides, answer choice (C) states that "ulcers can be produced in healthy individuals," and it does not specify that those individuals are human.

Yeah, I understand what you're saying about why A is wrong and why the ethics of C should be disregarded for this question, but sometimes the MCAT does actually throw stuff at you where an answer could be correct in principle, but not the correct answer for the mcat because it is inefficient or unethical or whatever. The fact that you have to disregard ethics for this question seems inconsistent to me and that's why it bugged me... and actually the answer choice says "healthy individuals and animals" so I think you're supposed to assume that the individuals are human...

 

[TooMuchResearch]

Yeah, I understand what you're saying about why A is wrong and why the ethics of C should be disregarded for this question, but sometimes the MCAT does actually throw stuff at you where an answer could be correct in principle, but not the correct answer for the mcat because it is inefficient or unethical or whatever. The fact that you have to disregard ethics for this question seems inconsistent to me and that's why it bugged me... and actually the answer choice says "healthy individuals and animals" so I think you're supposed to assume that the individuals are human...

My test just says healthy individuals in answer choice (C). No reference is made to human versus non-human individuals.