The Official June 2015 MCAT Thread

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i noticed that one too, stressingout. I ended up guessing correctly but i'm nearly certain they are both right.

I noticed a psychology question that i'm also fairly certain is wrong. About naloxone and heroin.
 
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stressingout said:
Perhaps I'm looking at the wrong question...are you talking about "what information about an axon is required to calculate.."

Because if you are and you're asking why radius isn't affected, I just related it to that equation R=pL/A. Hypothetically speaking, I would agree with you that the larger the diameter, the less resistance
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@timsk yeah this was the question.
Yup. This was exactly the line of reasoning i was struggling with in the exam. The radius expansion would be more pertinent considering its being squared in the denominator. What a mind ****.

I take that back now that i think of it the scale of things. The change in L is probably a few magnitudes larger.
 
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hmm, i was totally going to help you but then i saw you're referring to THAT question. I'm not sure i can explain it via a message board other than to say draw it out each step of the way. The starred CH3 from Acetyl CoA attachs the left carbonyl in acetoacetyl coa and then loses it's CoA. Then draw out each next step, keeping the stars on the marked carbons. Once i realized the first step that i just described i was able to see how the rest of the reaction proceeded. I hope it's the same for you!
 
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at some point i saw someone had posted a picture of them drawing out each step on the boards here somewhere...
 
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stressingout said:
Okay, so I'm reviewing a TPR test and this question is asking whether the image formed is real, virtual, inverted, or upright. The explanation says "since light must actually strike the film to expose it, the image must be real." I don't understand this reasoning if anyone could help me out. Does the presence of light automatically make the image real??
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Yeah an image is real only if the light rays actually travel and meet up at a point, rather than being reflected to that spot. So in that picture link, the dotted lines show where light has been reflected to, whereas the solid lines show where the light actually travels.

http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/imggo/virt3.gif
 
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timsk said:
hmm, i was totally going to help you but then i saw you're referring to THAT question. I'm not sure i can explain it via a message board other than to say draw it out each step of the way. The starred CH3 from Acetyl CoA attachs the left carbonyl in acetoacetyl coa and then loses it's CoA. Then draw out each next step, keeping the stars on the marked carbons. Once i realized the first step that i just described i was able to see how the rest of the reaction proceeded. I hope it's the same for you!
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Fair enough. What should I even study to remedy the fact that i got it wrong?
 
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yes! I had no idea we were supposed to know that...apparently primers are full of C & G. Now we know? And we now know that cytochrome c carries 1 e! 🙂
 
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timsk said:
yes! I had no idea we were supposed to know that...apparently primers are full of C & G. Now we know? And we now know that cytochrome c carries 1 e! 🙂
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Thats why i chose that choice. I was looking for start codons and stuff. I thought that was really tenuous.
Hey what do you think about Q54 in pysch. I believe they are utterly wrong.

edit. A. Medical record data is a terrible data source for studies.
B. Strict exclusion critieria are key to removing confounding variables and ensuring that you are studying a consistent population.
C. Exclusion of 10% of the sample is not terrible. Considering a large portion of cohort studies, survey studies, and RCTS have worse attrition or response rates.
 
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Hey Piii, can you expand on that? I guess i'm not too sure what the role of a primer is, so i'm not understanding the underlying logic?

I also thought C was a bit ridiculous. In longitudinal studies you'd love to have an attrition rate of less than 10%, but it's not too common. Therefore i can't imagine 10% of a 5000 sample being detrimental. Unless there was a link between all 500, like if they were all from the same hospital or same neighborhood. But if it's randomly distributed it shouldn't matter
 
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timsk said:
Hey Piii, can you expand on that? I guess i'm not too sure what the role of a primer is, so i'm not understanding the underlying logic?

I also thought C was a bit ridiculous. In longitudinal studies you'd love to have an attrition rate of less than 10%, but it's not too common. Therefore i can't imagine 10% of a 5000 sample being detrimental. Unless there was a link between all 500, like if they were all from the same hospital or same neighborhood. But if it's randomly distributed it shouldn't matter
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Sure! I assume you're familiar with PCR, yeah?

A primer is (usually, helicase serves as a primer in DNA replication) a sequence of nucleotides that are used to bind to DNA/RNA and initiate DNA/RNA synthesis. You design a primer to have a sequence complementary to a sequence of DNA that you want to specifically synthesize. Usually it is like a 40-60 base pair sequence that will anneal with single stranding DNA, then a polymerase comes and recognizes the double stranded pair and continues synthesizing from the primer.

In PCR, you must subject the samples to high temperate to 1) denature the DNA into single stranded copies, and 2) to activate the heat specific bacteria enzyme (usually Taq polymerase) which is only active at high temperatures, like 72 deg C.


Guanine and Cytosine nucleotides have 3 H bonds compared to A-T bonds.

Because of these high temperatures, a Primer with more CG pairs at the ends will be more protected from denaturing from their primed double stranded complex at high temperatures.

Hope that helps!
 
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Also #4 on AAMC FL psych section ... Why are they considering immediate recall after a word list as long term memory? I agree that long term and short term memory are separate entities, but wouldn't remembering a word list fall more under working memory?
 
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that's super helpful, thank you! If only we all had direct experience with all the concepts then this test would be so much easier. Learning from experience >> Learning from a book! 🙂
 
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Okazaki Frag Grenade said:
Also #4 on AAMC FL psych section ... Why are they considering immediate recall after a word list as long term memory? I agree that long term and short term memory are separate entities, but wouldn't remembering a word list fall more under working memory?
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I struggled with that question as well at first. And maybe Timsk can answer this better since he has more of a psych background. However, I cheated when i used the alzheimers patients data. Assuming the short term memory was intact for the Alzheimers group it seems like you can make the case that a seperate type of memory is functioning in the primacy vs recency effect. Although I always thought short and long term were much farther apart in duration. But it makes sense if you look at it like that then because the alzhiemers have an intact phonological loop. Also POE. A and B were wrong to begin with, and between c and D it was a toss up.
 
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timsk said:
one last thing, is the primer antisense to the target sequence of dna it is paired to?
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It has to be antisense to the DNA to pair up with it. However it doesnt necessarily have to contain the entire sequence just enough for the DNA pol to attach itself and do its thing.
 
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Okazaki Frag Grenade said:
Yeah an image is real only if the light rays actually travel and meet up at a point, rather than being reflected to that spot. So in that picture link, the dotted lines show where light has been reflected to, whereas the solid lines show where the light actually travels.

http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/imggo/virt3.gif
Click to expand...

Hmm so in virtual images, the light is reflected, while in real images, the light actually hits the spot? I totally missed that in my studies, thank you!
 
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timsk said:
one last thing, is the primer antisense to the target sequence of dna it is paired to?
Click to expand...

Correct, so when the PCR undergoes its thermocycling it sets the temp at around 55 degrees which is perfect for primer annealing (The Primer is complementary to the DNA sequence we want amplified) Taq pol will then find the primer and handle bizniz!
 
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i have no idea on that one tbh...i stared at it for quite a while. I sort of thing there is a mistake because, for the life of me, i cannot see how figure 2 says anything about long term memory, or anything in the passage for that matter. I also did POE and decided between B and D. B seemed even more of a stretch than D, so i guessed D. Sorry that's not very helpful :-/
 
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stressingout said:
Hmm so in virtual images, the light is reflected, while in real images, the light actually hits the spot? I totally missed that in my studies, thank you!
Click to expand...

Someone more intelligent can correct me on whether it's truly reflection. I just know that the important aspect is if the light actually reaches the point where the image is or not.
 
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Virtual images appear to be coming from a given location, but light is not actually being reflected from that spot. Whereas a real image, light is actually being reflected from the location of the image.

A standard mirror, for instance, is a virtual image. If you hold up a piece of paper in front of the mirror, no light will hit the paper (because no light is actually coming from where the image appears to be located). In a real image, however, if you held a piece of paper up between you and the real image, the light coming from the image would hit the paper and you would see the image on the paper.

Not sure if that helps at all, but that's how i learned it in my physics class.
 
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libertyyne said:
@timsk yeah this was the question.
Yup. This was exactly the line of reasoning i was struggling with in the exam. The radius expansion would be more pertinent considering its being squared in the denominator. What a mind ****.

I take that back now that i think of it the scale of things. The change in L is probably a few magnitudes larger.
Click to expand...

Oh I totally get what you're saying now! Area would be the square of r...now I'm confused. I get that the change in L is probably larger for that to be true, but how were we supposed to know that on the exam!?
 
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timsk said:
Virtual images appear to be coming from a given location, but light is not actually being reflected from that spot. Whereas a real image, light is actually being reflected from the location of the image.

A standard mirror, for instance, is a virtual image. If you hold up a piece of paper in front of the mirror, no light will hit the paper (because no light is actually coming from where the image appears to be located). In a real image, however, if you held a piece of paper up between you and the real image, the light coming from the image would hit the paper and you would see the image on the paper.

Not sure if that helps at all, but that's how i learned it in my physics class.
Click to expand...

Got it! Thank you!!
 
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timsk said:
i have no idea on that one tbh...i stared at it for quite a while. I sort of thing there is a mistake because, for the life of me, i cannot see how figure 2 says anything about long term memory, or anything in the passage for that matter. I also did POE and decided between B and D. B seemed even more of a stretch than D, so i guessed D. Sorry that's not very helpful :-/
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No worries! I give cognitive evaluation tests like that each day at work, so I think it just threw me off to hear long-term memory mentioned in regard to a recall task. But I guess the logic for that answer is kind of there in the graph, just not very clear.
 
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Okazaki Frag Grenade said:
Also #4 on AAMC FL psych section ... Why are they considering immediate recall after a word list as long term memory? I agree that long term and short term memory are separate entities, but wouldn't remembering a word list fall more under working memory?
Click to expand...
timsk said:
i have no idea on that one tbh...i stared at it for quite a while. I sort of thing there is a mistake because, for the life of me, i cannot see how figure 2 says anything about long term memory, or anything in the passage for that matter. I also did POE and decided between B and D. B seemed even more of a stretch than D, so i guessed D. Sorry that's not very helpful :-/
Click to expand...
upload_2015-6-14_22-0-19.png

IDK maybe I am reaching.
 
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timsk said:
one last thing, is the primer antisense to the target sequence of dna it is paired to?
Click to expand...
Yeah it is complementary or antisense, but keep in mind if you isolate a DNA from a cell, it's dsDNA. So in PCR you design two primers, one complimentary to the one strand on one side of the gene, and a second primer complementary to the other strand of DNA, on the OTHER side of the gene. So each PCR cycle you have synthesis of each strand of the dsDNA from each direction.

The synthesis ends with each elongation step, so you do like 32 cycles of and you get 2^32 strands of each DNA strand, theoretically.
 
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speaking of the psych portion #12. I know what confirmation bias is , I have no idea why that is pertinent. Any ideas?
 
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I dunno about your explanation for that question because the stem tells you specifically to look at only the non impaired data points. And i don't think that would explain it, i think it would just be a correlation. Because list recall is short term/working memory. But i could definitely be wrong about that. I do like how quick you come up with charts and graphs 🙂
 
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piii said:
Yeah it is complementary or antisense, but keep in mind if you isolate a DNA from a cell, it's dsDNA. So in PCR you design two primers, one complimentary to the one strand on one side of the gene, and a second primer complementary to the other strand of DNA, on the OTHER side of the gene. So each PCR cycle you have synthesis of each strand of the dsDNA from each direction.

The synthesis ends with each elongation step, so you do like 32 cycles of and you get 2^32 strands of each DNA strand, theoretically.
Click to expand...

Unless you're like me and completely neglect the existence of the reverse primer and leave it on the lab bench. I'll tell you one thing, I've never seen an entire research team stare at an RT-PCR plot with total confusion.
 
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timsk said:
I dunno about your explanation for that question because the stem tells you specifically to look at only the non impaired data points. And i don't think that would explain it, i think it would just be a correlation. Because list recall is short term/working memory. But i could definitely be wrong about that. I do like how quick you come up with charts and graphs 🙂
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I agree with you. Contrived ambiguous questions deserve contrived ambiguous answers.
 
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DocMarz47 said:
Unless you're like me and completely neglect the existence of the reverse primer and leave it on the lab bench. I'll tell you one thing, I've never seen an entire research team stare at an RT-PCR plot with total confusion.
Click to expand...

It's okay man, I squirted mouse bone marrow into my eye during an BM transplant :O
 
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Man the psych section is like verbal with a focus on study design. Thank god for graduate school. There is no way i would have been able to answer any of those study design questions in undergrad.
 
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libertyyne said:
So inPsych Q 47 who is integrated and who is segregated?
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Yeah this one was weird too. Apparently immigrants living in tight communities of other immigrants have protection from health disparities, so they're integrated I guess? But US born members of other ethnicities that do not live in these enclaves do not have the same protection, and thus face more health disparities and are more segregated. I dont know how we were supposed to know that though, as I dont remember reading that anywhere.
 
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piii said:
Is your goal MD or DO?
About the EK exams, I think if you score above 60% that is good. They are really hard.

CARS is great!
I'm a little worried about the other subjects. The Actual exam will for sure be harder in psych. Bio and chem are said to be about the same difficulty. I think you want to be >70% in your AAMC sample score.

How long have you prepared for? How much time have you put into practice passages, and how many have you done?
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About a month. Working full-time but I managed to get a week and a half to devote to full studying.

I think my big issue is that phys/chem I always feel like i'm rushing. I never have that problem in other sections particularly with CARS and psych. Anyone else feeling that way?
 
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yeah that was one i got wrong. I think it's sort of BS. Definitely being in ethnic enclaves can have protective effects, but it seems like an assumption to say one is segregated and one is not. I selected the answer choice about duration in the country.

It's hard to know...some times you get knocked for making assumptions based on information not stated in the passage. Other times they seem to require it, like in this one. Mixed messages!
 
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Okazaki Frag Grenade said:
Yeah this one was weird too. Apparently immigrants living in tight communities of other immigrants have protection from health disparities, so they're integrated I guess? But US born members of other ethnicities that do not live in these enclaves do not have the same protection, and thus face more health disparities and are more segregated. I dont know how we were supposed to know that though, as I dont remember reading that anywhere.
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I get that immigrants living in enclaves get the benefit of the healthy immigrant effect. And tight knit communities may be responsible for some of that effect. I was just super confused as to what the Q stem was reffering to. Were they asking why the immigrants were protected? or why the nationals were not protected? Which frame of reference?
 
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timsk said:
yeah that was one i got wrong. I think it's sort of BS. Definitely being in ethnic enclaves can have protective effects, but it seems like an assumption to say one is segregated and one is not. I selected the answer choice about duration in the country.

It's hard to know...some times you get knocked for making assumptions based on information not stated in the passage. Other times they seem to require it, like in this one. Mixed messages!
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It seems like stand alones are free game for outside information. Haha that and when they are asking you to pick a surrealist item out of a list. I picked that lobster soo quick my mouse stopped working.
 
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suednym said:
About a month. Working full-time but I managed to get a week and a half to devote to full studying.

I think my big issue is that phys/chem I always feel like i'm rushing. I never have that problem in other sections particularly with CARS and psych. Anyone else feeling that way?
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This might just be me. I would not recommend sitting for the mcat after a month of studying. MD schools usually have a 80th percentile for interviews and 85-90 percentile for matriculants. DO schools i believe it is closer to 27. That being said 504 is around that and 508 is around what the 30 would theoretically be. If you are working full time i would recommend 4-6 months of prep. The rule for the old exam was 300 hours. The new exam is probably going to be 350-400 considering an added section. You want to take this exam only once in your life. You want to make it count.
 
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libertyyne said:
This might just be me. I would not recommend sitting for the mcat after a month of studying. MD schools usually have a 80th percentile for interviews and 85-90 percentile for matriculants. DO schools i believe it is closer to 27. That being said 504 is around that and 508 is around what the 30 would theoretically be. If you are working full time i would recommend 4-6 months of prep. The rule for the old exam was 300 hours. The new exam is probably going to be 350-400 considering an added section. You want to take this exam only once in your life. You want to make it count.
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Stop scaring me! I've only study for a little over a month as well
 
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libertyyne said:
It seems like stand alones are free game for outside information. Haha that and when they are asking you to pick a surrealist item out of a list. I picked that lobster soo quick my mouse stopped working.
Click to expand...

I think your'e probably right about that. In my binder of questions/concepts i've missed i have some notes to me saying assume nothing, some telling that assuming is okay. I think i'll add your qualifier!

And i second your thought about trying to get more study time before taking the test suednym. I've been studying for 6 months and still feel like i could benefit from another month or two. Granted i've been out of school for some time. Plus work and all the rest. I think i'll have put in about 400-450 hours. Have i mentioned how excited i am to get this damn thing over with?!

To the rushing point, i'd imagine phys/chem is everyone's slowest section as it requires calculations and manipulations.
 
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libertyyne said:
Question number 9 on the AAMC FL. I got it right, but why wouldnt the expansion of the diameter due to heating not reduce the resistance?
Click to expand...
An increase in temperature increases the kinetic energy of the particles in all directions thereby interfering with current. Temperature increases resistance on its own.
 
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