the main usable product of the TCA cycle is

[mj6969]

The main, usable product of the tricarboxylic acid cycle is

Energy
Carbon dioxide
The reduced coenzymes NADH+H+ and FADH2
Malate

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[Vihsadas]

aha! Makes sense!!!!

so, choice B and D are wrong for "similar" reasons? i.e you cannot produce more NADH (change the cycle) nor you can do more cycles which will affect the system.

Yes that's right. This problem exemplifies the trickiness that the MCAT can present. In B and D its suggesting a fundamental change to the cycle, which by the wording of the question, would make the answers 'false'. C, however, does not say 'make the malate aspartate shuttle more efficient', or 'transport an extra NADH via the malate-aspartate shuttle,' which would also make answer C 'false'. It suggests, instead, an entirely new shuttle, which is more efficient, making this answer 'plausible'.
This is how the MCAT tests 'logic' and 'knowledge'. On this problem if you had the 'knowledge' of information that is extranneous to the MCAT but related to this in real life, you would be able to answer the question. However, if you didn't have that knowledge, and only had the knowledge of your MCAT concept review books by using the 'logic' that I outlined you could still figure it out.

 

[Mandek]

Yes that's right. This problem exemplifies the trickiness that the MCAT can present. In B and D its suggesting a fundamental change to the cycle, which by the wording of the question, would make the answers 'false'. C, however, does not say 'make the malate aspartate shuttle more efficient', or 'transport an extra NADH via the malate-aspartate shuttle,' which would also make answer C 'false'. It suggests, instead, an entirely new shuttle, which is more efficient, making this answer 'plausible'.
This is how the MCAT tests 'logic' instead of 'knowledge'. On this problem if you had the 'knowledge' of information that is extranneous to the MCAT but related to this in real life, you could still answer the question. However, if you didn't have that knowledge, and only had the knowledge of your MCAT concept review books by using the 'logic' that I outlined you could still figure it out.

wow....yes thanks...I truly believe that the more practice MCAT problems you do, the more you find out how MCAT tests you and you get the right thought process which will in turn help you on real MCAT. Even though questions wont be the same, it still would be very helpful to know what kind of questions are asked on MCAT, and thus the more practice you do, the closer it brings you to your goal (of what set goal one has for the MCAT score).

 

[Vihsadas]

wow....yes thanks...I truly believe that the more practice MCAT problems you do, the more you find out how MCAT tests you and you get the right thought process which will in turn help you on real MCAT. Even though questions wont be the same, it still would be very helpful to know what kind of questions are asked on MCAT, and thus the more practice you do, the closer it brings you to your goal (of what set goal one has for the MCAT score).

That's exactly right. At a certain point, answering some questions almost becomes a 'learned art'. You know, that question you just asked, when I first glanced at each answer I just kinda 'felt' that C seemed more right, and the others were more wrong. Then when I sat down to think about it, I rationalized why. This is pure practice. You practice the problems more and more, you'll begin to develop what I call 'MCAT intuition'.

 

[Mandek]

That's exactly right. At a certain point, answering some questions almost becomes a 'learned art'. You know, that question you just asked, when I first glanced at each answer I just kinda 'felt' that C seemed more right, and the others were more wrong. Then when I sat down to think about it, I rationalized why. This is pure practice. You practice the problems more and more, you'll begin to develop what I call 'MCAT intuition'.

Do you think this also applies to the VR section? Did you notice similar traps thrown on the MCAT to the practice exams (in verbal that is)?

 

[Vihsadas]

Do you think this also applies to the VR section? Did you notice similar traps thrown on the MCAT to the practice exams (in verbal that is)?

Yes definitely. It applies more so to the VR. In the AAMC practice exams (which can be MUCH easier than your real exam if you get a bad exam day!!) a large part of the reason I was scoring consistently in the 13-15 was because I had very good intuition about the problems. Check out my VR tips. They are somewhere on this forum.

As a corollary to VR, I'd say that you really, really need to make sure that you can do the practice AAMC exams in 6.5-7mins per passage rather than 8. If you have 10-15mins left over during your initial run through on the AAMC exams, you should be ok. Just be AWARE that your real VR *Could* be longer, harder, and more confusing than the AAMC practices.

 

[Mandek]

Yes definitely. It applies more so to the VR. In the AAMC practice exams (which can be MUCH easier than your real exam if you get a bad exam day!!) a large part of the reason I was scoring consistently in the 13-15 was because I had very good intuition about the problems. Check out my VR tips. They are somewhere on this forum.

As a corollary to VR, I'd say that you really, really need to make sure that you can do the practice AAMC exams in 6.5-7mins per passage rather than 8. If you have 10-15mins left over during your initial run through on the AAMC exams, you should be ok. Just be AWARE that your real VR *Could* be longer, harder, and more confusing than the AAMC practices.

Yes, thanks!!!!! I always wanted to ask you: how did you feel on each section after you walked out of the real MCAT? Were you pretty confident/sure about getting 13-15's on PR and BS, and how did you feel on VR. I know you said VR was tough, but alot of times I've heard people say they almost wanted to void/cancel their scores after walking out of the real MCAT but it turned out to be a 32-33+ for them ....weird

 

[Vihsadas]

Yes, thanks!!!!! I always wanted to ask you: how did you feel on each section after you walked out of the real MCAT? Were you pretty confident/sure about getting 13-15's on PR and BS, and how did you feel on VR. I know you said VR was tough, but alot of times I've heard people say they almost wanted to void/cancel their scores after walking out of the real MCAT but it turned out to be a 32-33+ for them ....weird

Yeah. It was similar for me. After my PS (first section) I remember walking out to get a candy bar and thinking "Holy crap. I think I just got everything right." After walking out of my VR I was completely shaken. Seriously one of the most horrifying experiences of my life. haha. I had never taken any practice test that hard. That VR section kicked my butt. I felt like voiding my test after that to be certain...I feel like if I had taken it in August, I actually maybe WOULD have voided my score (Imagine that!).
After BS, I remember thinking "Oh crap. I think I got them all rig...oh wait. Damnit. I missed one."

So on BS and PS I knew I got a 14 and a 15, on VR, I seriously thought I got a 7 or 8. I feel like if that section was curved like the practice MCATs I would have!

 

[Mandek]

Yeah. It was similar for me. After my PS (first section) I remember walking out to get a candy bar and thinking "Holy crap. I think I just got everything right." After walking out of my VR I was completely shaken. Seriously one of the most horrifying experiences of my life. haha. I had never taken any practice test that hard. That VR section kicked my butt. I felt like voiding my test after that to be certain...I feel like if I had taken it in August, I actually maybe WOULD have voided my score (Imagine that!).
After BS, I remember thinking "Oh crap. I think I got them all rig...oh wait. Damnit. I missed one."

So on BS and PS I knew I got a 14 and a 15, on VR, I seriously thought I got a 7 or 8. I feel like if that section was curved like the practice MCATs I would have!

I guess fair enough, if you found VR hard, then it really was hard and curve did justice...in order to get a 10 on normal curve, you have to get 28 right out of 40 i believe. do you think its possible in a VR section hard like that (the one you had on real thing) to get 15-17 wrong and still end up with a 10 since it was harder? haha

no idea how AAMC comes up with a "curve"

 

[tncekm]

It essentially transports the NADH produced in glycolysis into the ETC. The inner mitochondrial membrane is not permeable to NADH or H+, hence the need for a special "shuttle." This is why the NADH in glycolysis only produce 2 ATP while all (from pyruvate decarbox & ETC) the other NADH produce 3 ATP...

Just to help illuminate "why" NADH from Glycolysis and FADH2 only produce, the NADH produced by Glycolysis is not delivered to the NADH Dehydrogenase complex, its skips it, as does FADH2. NADH from the krebs cycle does go through the NADH dehydrogenase complex. So, normally NADH hits 3/3 complexes and FADH2 and NADH from glycolysis only get 2/3, therefore, they result in 2/3 the ATP.