MCAT Bio..What to Expect..Hope this Helps

[Knocked Up]

Ok, I'm not a bad guy. I preach that the MCAT is by far the most important aspect of your application, but I never actually post on this side of the forum. I've got some time to kill before med school starts in the fall, and I just finished a paper. I decided to post the abstract and ask a few questions to show you guys what skills you need for the "new" MCAT Bio before I got out tonight. I hope this helps. Passage below and some questions after that.

------------------

Inflammation is linked clinically and epidemiologi- cally to cancer, and NF-kB appears to play a causa- tive role, but the mechanisms are poorly understood. We show that transient activation of Src oncoprotein can mediate an epigenetic switch from immortalized breast cells to a stably transformed line that forms self-renewing mammospheres that contain cancer stem cells. Src activation triggers an inflammatory response mediated by NF-kB that directly activates Lin28 transcription and rapidly reduces let-7 micro- RNA levels. Let-7 directly inhibits IL6 expression, re- sulting in higher levels of IL6 than achieved by NF-kB activation. IL6-mediated activation of the STAT3 transcription factor is necessary for transformation, and IL6 activates NF-kB, thereby completing a posi- tive feedback loop. This regulatory circuit operates in other cancer cells lines, and its transcriptional signature is found in human cancer tissues. Thus, inflammation activates a positive feedback loop that maintains the epigenetic transformed state for many generations in the absence of the inducing signal.

-------------------

1) First, whenever you see a passage like this ALWAYS draw out the pathway. So do just that. Use --> for stimulates and ---l for inhibits.

2) Based on the passage how can NfkB be classified.
a) a restriction factor
b) a transcription factor
c) a DNA methyl transferase
d) a cytokine

3) If the scientists in the passage had over expressed in let 7 in the cell lines, what effect would this have on cellular transformation.
a) It would increase levels of cellular transformation.
b) Decrease levels of cellular transformation.
c) Have no effect since IL6 positively feedbacks on NFKB leading to cellular transformation regardless of let 7.
d) WTF? Who cares, these questions are nothing like the Kaplan tests...

4) Overexpression of SRC in cell lines of Stat 3 -/- mice would have which of the following effects?
a) Epigenetic switch leading to increased cellular transformation.
b) Decreased expression of Lin28.
c) Lower levels of inflammation due to down regulation of IL6.
d) Increased levels in Lin28 and IL6, yet no epigenetic switch to cellular transformation.

5) Which of the following statements is false?
I) The mechanistic regulation of cellular transformation described is dependent on changes in DNA sequences of target genes.
II) IL6 positively feedbacks on NFKB.
III) Overexpression of Lin28 in breast cells leads to increased levels of cellular transformation.

a) I
b) II
c) III
d) I and III
e) II and III
f) I and II

---

Members don't see this ad.

 

[bdc142]

It's definitely been said before, but if you happen to be taking the MCAT a year later or whatever - take a class in cell biology or biochem. They go over pathways and data from experiments to teach concepts (like this question) and when you take time to understand them in class...this stuff won't be as difficult.

(I haven't actually taken the real MCAT yet, but I got 14's on AAMC 10/11 if that counts and I thought Ebola and other similar pathway questions were straightforward)

 

[ridethecliche]

It's definitely been said before, but if you happen to be taking the MCAT a year later or whatever - take a class in cell biology or biochem. They go over pathways and data from experiments to teach concepts (like this question) and when you take time to understand them in class...this stuff won't be as difficult.

(I haven't actually taken the real MCAT yet, but I got 14's on AAMC 10/11 if that counts and I thought Ebola and other similar pathway questions were straightforward)

No it doesn't really help because you learn stuff like that in intro bio and molecular bio as well.

Biochemistry is very memorization based. Sure it might be helpful, but on the MCAT you don't have to know that xyz enzyme works by transferring a proton between asp 142 and glu 154. I think that stuff is awesome, but it is really nothing like the way the MCAT is tested or should be taught.

At times I wonder if less knowledge is actually beneficial since then there is less outside information for you to draw from and screw things up.

 

[bdc142]

No it doesn't really help because you learn stuff like that in intro bio and molecular bio as well.

Biochemistry is very memorization based. Sure it might be helpful, but on the MCAT you don't have to know that xyz enzyme works by transferring a proton between asp 142 and glu 154. I think that stuff is awesome, but it is really nothing like the way the MCAT is tested or should be taught.

At times I wonder if less knowledge is actually beneficial since then there is less outside information for you to draw from and screw things up.

Intro bio textbooks only cover extremely simple experiments. At least my cell bio and biochem classes went over concepts by looking at raw data from experiments (gels etc.) or just literally giving us a slide of certain pathways with all your fancy enzyme A, B, etc. Learning how to read these pathways and interpreting experiments from these classes have helped me at least (crossing fingers for upcoming MCAT )

 

[ridethecliche]

Intro bio textbooks only cover extremely simple experiments. At least my cell bio and biochem classes went over concepts by looking at raw data from experiments (gels etc.) or just literally giving us a slide of certain pathways with all your fancy enzyme A, B, etc. Learning how to read these pathways and interpreting experiments from these classes have helped me at least (crossing fingers for upcoming MCAT )

I did all that stuff in my intro bio lab.

Biochem isn't as helpful as people make it out to be. You do tons of reaction-y stuff in organic chem. The logic is the same.

 

[shoenberg3]

Having taken the 5/19 BS section, I can say that this passage is far easier than at least two of the passages on the actual MCAT.

 

[kasho11]

I remember going through Kaplan's mapping strategy and thinking this is stupid I don't need it. Doing the AAMCs I thought for the most part it was stupid and I didn't need it and I've done well on those. For the real thing - for every section - I am going to at least write down the main topic of the passage for each section, like PS experiment in optics with electron stuff, for verbal I probably won't map, maybe just write down the key thought of the passage and of each paragraph.

For bio though, any pathway passages I will diagram, for any experimental passages I will diagram and put into simple words. Instead of Cut J412D at site 2d4 with RQ79 and combined DerpDeepHardword and performed post-introduction ligation with (#*$@(82. I will write Bacteria chromosome cut at place A with restriction enzyme 1, added in plasmid 1 and closed with ligase enzyme 2. Or something like that. Taking it Thursday so we'll see how I feel doing this. Then we'll see how I actually did compared to how I felt.

 

[Trayshawn]

Let-7 directly inhibits IL6 expression, re- sulting in higher levels of IL6 than achieved by NF-kB activation.

This sentence makes no sense. If let-7 INHIBITS IL6 expression, then how the heck does it INCREASE levels of IL6? Is there a typo here?

 

[Testosterone]

This sentence makes no sense. If let-7 INHIBITS IL6 expression, then how the heck does it INCREASE levels of IL6? Is there a typo here?

Because the sentence before it says that lin28 reduces let-7.

 

[LianaStan]

When did this shift into the 'new' Bio section as put forth by the OP happen?

Also, is this new BS section more passage and analysis oriented as opposed to direct recall of information? And are most people who have taken the MCAT recently in agreement that the AAMC practice tests have very different BS sections than the actual BS?

 

[newmember1]

Bump.

This passage was great practice for my recent MCAT. Now that we are down to only one more MCAT before the season ends, would all those who took it this summer agree with the OP's analysis and passage style. I know I would.

 

[MAnne]

Wow after writing the pathways I got them all correct! I started to do that for the 9/1 exam but some of them I wasn't even sure how to write the pathways because I felt like I was running into too many U-turns (stupid NE traffic pattern). I really need to find some more practice. This is great if you can post more of these. Maybe a blog??


~M

 

[OCDOCDOCD]

Bump.

This passage was great practice for my recent MCAT. Now that we are down to only one more MCAT before the season ends, would all those who took it this summer agree with the OP's analysis and passage style. I know I would.

I wouldn't say it's very good at all. My test was heavily experimental and people who took it thought it was harder than any of the AAMCs, and none of the passages looked anything like this.

I stand by what I said months ago in this thread: OP's passage uses far too many technical terms for an MCAT passage, or at least uses them without any explanation. For example, terms like "transient activation", "mammosphere", "epigenetic", and "transformed state" are not going to show up on a passage without a line explaining what each one means. While you may be familiar with these terms through upper level bio courses, the MCAT assumes you only took intro bio (I would also argue it assumes you took biochemistry, but that's a topic for a different thread).

Furthermore, there's too much molecular biology. While my test did have molecular bio passages on it, they didn't launch into a rapid-fire name-off of each one like OP's passage does. Nor did they mention too many molecules you had to keep track off. You're looking at about 2-3 different molecules to keep track off on a passage, and the passage will give you a short description of each one. I think I may have mapped one passage like OP suggested, and it turned out to be totally unnecessary.

OP's questions are also too advanced. The thing about MCAT bio is that it's testing simple concepts but in a roundabout way. To quote from a post I previously made:

- Part of a passage may detail an experiment in which an experimenter isolated a mutant protein and ran it on an electrophoresis gel along with the wildtype protein. He found that the mutant protein traveled twice as far as the wildtype protein. A question might then ask you what kind of gene mutation most likely caused the altered protein, to which the answer would be "nonsense mutation". Essentially all this question was asking was "what kind of mutation creates a shorter version of a protein?"

- A passage may talk about the effects of a peptide hormone Y (let's say it causes a cell to release another substance, hormone X), and then talk about how during an experiment an experimenter administered a receptor antagonist in vitro. It will then give you a graph showing hormone X vs hormone Y concentrations with two lines, one for the control condition and another for the antagonist condition. The graph shows that for the control condition the line increases linearly and then hits an asymptote. Meanwhile the antagonist condition shows that the line increases linearly for a fraction of the time as the control group and then hits an asymptote at a level of hormone Y 1/5th that of the control group. The passage might then ask what kind of antagonist was used, to which the correct answer would be "allosteric inhibitor". All this question was asking was "what kind of inhibitor can't be overcome with increased substrate concentration?"

Contrast this to OP's questions which aren't testing any basic concepts, but are instead testing how well you can follow a pathway.

There are other issues with OP's passage as well: it's too short and there's no graphs or tables. But these are relatively minor compared to the above and I'm not going to expound on them.

I would argue against conventional SDN wisdom that there's no good practice for BS and you'll be blindsided when you take the test. That isn't true at all. The TPRH SW bio passages are all pretty good practice for BS. The AAMCs, at least 7 and up, are also, imo, not too far off the mark (especially AAMC 11, and not just because of the ebola passage), although if my MCAT was any indication of the usual trend the non-experimental passages are pretty hard to come by these days. The Kaplan BS section tests are also pretty good. Finally, the MCAT Official Guide was practically a sneak peak of my test; the content obviously wasn't the same, but the style of the passages and questions were nearly identical.

 

[tttgo]

I just want to say that this is AMAZING advice. This is why I think getting content down and doing lots of passages and thoroughly analyzing would be more effective than reading random science articles that might not have the mcat thinking style.

I wouldn't say it's very good at all. My test was heavily experimental and people who took it thought it was harder than any of the AAMCs, and none of the passages looked anything like this.

I stand by what I said months ago in this thread: OP's passage uses far too many technical terms for an MCAT passage, or at least uses them without any explanation. For example, terms like "transient activation", "mammosphere", "epigenetic", and "transformed state" are not going to show up on a passage without a line explaining what each one means. While you may be familiar with these terms through upper level bio courses, the MCAT assumes you only took intro bio (I would also argue it assumes you took biochemistry, but that's a topic for a different thread).

Furthermore, there's too much molecular biology. While my test did have molecular bio passages on it, they didn't launch into a rapid-fire name-off of each one like OP's passage does. Nor did they mention too many molecules you had to keep track off. You're looking at about 2-3 different molecules to keep track off on a passage, and the passage will give you a short description of each one. I think I may have mapped one passage like OP suggested, and it turned out to be totally unnecessary.

OP's questions are also too advanced. The thing about MCAT bio is that it's testing simple concepts but in a roundabout way. To quote from a post I previously made:

- Part of a passage may detail an experiment in which an experimenter isolated a mutant protein and ran it on an electrophoresis gel along with the wildtype protein. He found that the mutant protein traveled twice as far as the wildtype protein. A question might then ask you what kind of gene mutation most likely caused the altered protein, to which the answer would be "nonsense mutation". Essentially all this question was asking was "what kind of mutation creates a shorter version of a protein?"

- A passage may talk about the effects of a peptide hormone Y (let's say it causes a cell to release another substance, hormone X), and then talk about how during an experiment an experimenter administered a receptor antagonist in vitro. It will then give you a graph showing hormone X vs hormone Y concentrations with two lines, one for the control condition and another for the antagonist condition. The graph shows that for the control condition the line increases linearly and then hits an asymptote. Meanwhile the antagonist condition shows that the line increases linearly for a fraction of the time as the control group and then hits an asymptote at a level of hormone Y 1/5th that of the control group. The passage might then ask what kind of antagonist was used, to which the correct answer would be "allosteric inhibitor". All this question was asking was "what kind of inhibitor can't be overcome with increased substrate concentration?"

Contrast this to OP's questions which aren't testing any basic concepts, but are instead testing how well you can follow a pathway.

There are other issues with OP's passage as well: it's too short and there's no graphs or tables. But these are relatively minor compared to the above and I'm not going to expound on them.

I would argue against conventional SDN wisdom that there's no good practice for BS and you'll be blindsided when you take the test. That isn't true at all. The TPRH SW bio passages are all pretty good practice for BS. The AAMCs, at least 7 and up, are also, imo, not too far off the mark (especially AAMC 11, and not just because of the ebola passage), although if my MCAT was any indication of the usual trend the non-experimental passages are pretty hard to come by these days. The Kaplan BS section tests are also pretty good. Finally, the MCAT Official Guide was practically a sneak peak of my test; the content obviously wasn't the same, but the style of the passages and questions were nearly identical.

 

[Czarcasm]

Lol, sweet. Got all OP's questions right. Thought this was useful and worthy of a bump.