EK 1001 Bio Q

[tncekm]

Okay, so I was going over Passage #501, and although there are quite a few questions I've found in Bio 1001 that are poorly posed, I think this is a topper.

Relevant background information given: Albumin is a major osmoregulatory protein in the plasma. (Yes, we knew that already, thanks EK.)

451. Albumin is a critical factor in determining colloid osmotic pressure. Which other plasma protein can be utilized as a transporter of lipid hormones?

A. fibrinogen
B. myosin
C. C peptide
D. F-actin

Highlight below this text to see the answer.
A. fibrinogen; Yes, I know its a plasma protein, but what the hell does it have to do with lipid hormone transport? The passage didn't have ANYTHING to say about that, either.

So, did anyone else find that questions absolutely ridiculous? I didn't see anything remotely close to being this "out there" on AAMC 3, so I'm really hoping that I won't find anything like that on any actual (practice) MCAT's.

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[tncekm]

Edit: oops.

 

[iA-MD2013]

I would have never gotten the answer to this...but now that I know it, maybe I can explain it...
So, in tpr they say that steroid hormones are transported through the blood by forming weak van der waals forces with plasma proteins since they are insoluble. The example tpr gave was albumin. I'm guessing fibrinogen would be another protein that could do the same. What do you think?
btw, thats great how you highlight to see the answer...good idea!

 

[tncekm]

Yeah, I figure it has to work something like that, and I could see how hydrophobic and van der walls interactions (primarily hydrophobic though--I think its important to know that transport proteins bind to lipids via hydrophobic interactions) could contribute ANY plasma protein functioning as a lipid hormone carrier, but it was smashed into our heads that "fibrinogen is for clotting". I figured it was a "trick question" when they included Peptide C, which I chose. Here was my reasoning:

Fibrinogen -- involved in clotting, as we should know and were told to study by EK
Myosin -- found in the muscles exclusively, ruled out
Protein C -- by process of elimination, I figured that a) it needed to be a protein, and b) the other three choices seemed poor, so it had to be this one. Alas, I was wrong!
F-actin -- not much information is given, sounds like a protein, but could be anything.

Overall, I'm averaging slightly less than 80% correct over the 7 or so EK bio passages I've done, and its primarily stuff like this that's killing me. Its very frustrating. But, I guess its good for critical thinking ?

 

[iA-MD2013]

Yeah, I figure it has to work something like that, and I could see how hydrophobic and van der walls interactions (primarily hydrophobic though--I think its important to know that transport proteins bind to lipids via hydrophobic interactions) could contribute ANY plasma protein functioning as a lipid hormone carrier, but it was smashed into our heads that "fibrinogen is for clotting". I figured it was a "trick question" when they included Peptide C, which I chose. Here was my reasoning:

Fibrinogen -- involved in clotting, as we should know and were told to study by EK
Myosin -- found in the muscles exclusively, ruled out
Protein C -- by process of elimination, I figured that a) it needed to be a protein, and b) the other three choices seemed poor, so it had to be this one. Alas, I was wrong!
F-actin -- not much information is given, sounds like a protein, but could be anything.

Overall, I'm averaging slightly less than 80% correct over the 7 or so EK bio passages I've done, and its primarily stuff like this that's killing me. Its very frustrating. But, I guess its good for critical thinking ?

Yeah, I would have done the same thing and probably ended up with the same answer. I doubt we'll see a question like that on the mcat...it is good for the critical thinking though. I still think it's a pretty crappy question. ehhh, it's all practice, right?

 

[tncekm]

Yeah, it is... I just like seeing 100%'s, and when I get questions like that, I don't see those three beautiful numbers!

 

[iA-MD2013]

Yeah, it is... I just like seeing 100%'s, and when I get questions like that, I don't see those three beautiful numbers!

You should just do what I do. If you get the answer wrong, it was a stupid question. If you get the answer right, you're smart as hell. That way, you're always right!

 

[tncekm]

That's my approach to verbal.

 

[Cool Aberration]

That's my approach to life.

 

[phospho]

Yeah, I figure it has to work something like that, and I could see how hydrophobic and van der walls interactions (primarily hydrophobic though--I think its important to know that transport proteins bind to lipids via hydrophobic interactions) could contribute ANY plasma protein functioning as a lipid hormone carrier, but it was smashed into our heads that "fibrinogen is for clotting". I figured it was a "trick question" when they included Peptide C, which I chose. Here was my reasoning:

Fibrinogen -- involved in clotting, as we should know and were told to study by EK
Myosin -- found in the muscles exclusively, ruled out
Protein C -- by process of elimination, I figured that a) it needed to be a protein, and b) the other three choices seemed poor, so it had to be this one. Alas, I was wrong!
F-actin -- not much information is given, sounds like a protein, but could be anything.

Overall, I'm averaging slightly less than 80% correct over the 7 or so EK bio passages I've done, and its primarily stuff like this that's killing me. Its very frustrating. But, I guess its good for critical thinking ?

I thought of it this way:

Like you said, C and D are definitely out.

However, fibrinogen is technically an oligosaccharide. It's basically a glycoprotein. So we know it's soluble in our plasma.

On the other hand, myosin is a globulin, so it's not that soluble. It can't be the answer since we need something that is actually soluble in plasma to be able to transport anything.

hope that helps

 

[RSAgator]

I thought of it this way:

Like you said, C and D are definitely out.

However, fibrinogen is technically an oligosaccharide. It's basically a glycoprotein. So we know it's soluble in our plasma.

On the other hand, myosin is a globulin, so it's not that soluble. It can't be the answer since we need something that is actually soluble in plasma to be able to transport anything.

hope that helps

How could you rule out C?

I would have picked C as well. A and D I would have ruled out, and then it would have been a toss up between B and C. I would have thought "fibrinogen is for clotting so probably C." I think it's a bit out of the scope of the MCAT and if a question like this was asked it would likely not require such esoteric knowledge (at least that's what I hope).

edit: What are C-peptides anyway?

 

[iA-MD2013]

How could you rule out C?

I would have picked C as well. A and D I would have ruled out, and then it would have been a toss up between B and C. I would have thought "fibrinogen is for clotting so probably C." I think it's a bit out of the scope of the MCAT and if a question like this was asked it would likely not require such esoteric knowledge (at least that's what I hope).

edit: What are C-peptides anyway?

I would rule it out because I've never heard of it before!
From Wikipedia:
http://en.wikipedia.org/wiki/C-peptide

 

[travelbug73]

I don't know that it is very logical but this is why I picked A:

Myosin and Actin: Associated with muscle contraction and the cytoskeleton

C-peptide: did not know what it was

Fibrinogen: Only one among the answer choices that is related to plasma/blood and hence picked it

 

[RSAgator]

I don't know that it is very logical but this is why I picked A:

Myosin and Actin: Associated with muscle contraction and the cytoskeleton

C-peptide: did not know what it was

Fibrinogen: Only one among the answer choices that is related to plasma/blood and hence picked it

logical only because you got the right answer hehe. Fibrinogen being associated with the blood makes it plausible, but without knowing c-peptide you can't rule it out. By your "logic" it could potentially be any peptide that travels in the blood. Regardless, I think it's a bad question =P

 

[travelbug73]

logical only because you got the right answer hehe. Fibrinogen being associated with the blood makes it plausible, but without knowing c-peptide you can't rule it out. By your "logic" it could potentially be any peptide that travels in the blood. Regardless, I think it's a bad question =P

You misread me: I said, "I don't know that it is very logical", maybe I should have said I don't think it is logical, regardless, I did not claim it to be logical and I completely agree that it was a poor question. I also concur with the above posters that a good part of the book suffers from the problem of poorly worded questions and questions not related to the passage.

 

[phospho]

How could you rule out C?


edit: What are C-peptides anyway?

You just answered your own question

I ruled out C because I've never heard about it.

 

[RSAgator]

You just answered your own question

I ruled out C because I've never heard about it.

bah =P

 

[tncekm]

I don't know that it is very logical but this is why I picked A:

Myosin and Actin: Associated with muscle contraction and the cytoskeleton

C-peptide: did not know what it was

Fibrinogen: Only one among the answer choices that is related to plasma/blood and hence picked it

Its good logic, IMO. I just got thrown off, largely, because Fibrinogen was described in all of my texts as "specifically" a clotting agent.

One thing I Just noticed was I didn't see the "actin" part of F-actin, LOL. It wouldn't have changed my answer, but I still can't believe I didn't notice that!

 

[coffeebythelake]

I agree the wording is poor. That is a very difficult question for MCAT. Most medical students would have problems trying to answer it. BTW, C peptide is cleaved from proinsulin to make insulin.

 

[tncekm]

I agree the wording is poor. That is a very difficult question for MCAT. Most medical students would have problems trying to answer it. BTW, C peptide is cleaved from proinsulin to make insulin.

That means it is also a plasma protein, right? So, theoretically its no more incorrect than Fibrinogen, right?

 

[mterp45]

I would rule it out because I've never heard of it before!

funny.

 

[coffeebythelake]

That means it is also a plasma protein, right? So, theoretically its no more incorrect than Fibrinogen, right?

To clarify my previous statement, proinsulin is broken into C-peptide and insulin molecules. Not sure if it qualifies as a plasma protein, since it is not in constant circulation.

 

[sicboy188]

can't you reword the question as: "Which of the following are plasma proteins?"

ive noticed that EK's questions ask something that is not expected to know, and once you acknowledge that, you can eliminate answer choices based on certain modifiers in the question stem.

Given that this is an EK tactic, does the real MCAT utilize this? seems kinda dirty.

FYI: i would eliminated it down to A and C and went with A just because i know fibrinogen is a plasma protien

 

[tncekm]

Yeah, you could reword it like that, but throwing C peptide in there really was tricky. Most peptides are water soluble and therefore could easily have been a transporter molecule. Given that it was pounded into our heads that fibrinogen was a clotting factor, I figured this must have been one of those tricky "process of elimination" questions, but I guessed wrong.

I've taken 3 practice tests (only one of them was AAMC) and none of the answers to questions have been this ambiguous.

 

[sicboy188]

i totaly agree with you. this question is pretty lame. All in all, its a didactic tool by EK to make you think without freaking out... albeit a pretty wack didactic tool...

its reassuring that this hasnt come up in your practice. Ive taken kaplan FL 1-4 and have yet to see something like this too...