TBR Bio Cells and Viruses Psg VII #42

[erythrocyte666]

See question attached. Answer is C.
I know cholesterol prevents membrane crystallization at lower temperatures by interfering with the phospholipid packing.
But doesn't cholesterol decrease membrane fluidity, especially at higher temperatures?

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[ohkos1]

I would have just put C, because like you said cholesterol both increases and decreases fluidity. Since cholesterol broadens the phase change, III is always true, while I is sometimes true.

 

[amy_k]

I agree with ohkos1, the presence of cholesterol only decreases fluidity at higher temperatures as the original post mentioned, and since we are not told anything about the temperature we cannot make any assumptions about cholesterol. They are definitely trying to trick you into putting I and III there.

 

[erythrocyte666]

But then nothing is said about the membrane being at lower temperature. Maybe the question is a bit ambiguous?

 

[ohkos1]

But then nothing is said about the membrane being at lower temperature. Maybe the question is a bit ambiguous?

I do this too and it's a bad habit I'm trying to fix for the tests. Sometimes I bring in too much outside knowledge that I make assumptions that aren't there. Even AAMC questions seem vague because I think it feels like it can go either way. However, it's really important to just answer what's given and not go beyond and make assumptions.

 

[erythrocyte666]

I do this too and it's a bad habit I'm trying to fix for the tests. Sometimes I bring in too much outside knowledge that I make assumptions that aren't there. Even AAMC questions seem vague because I think it feels like it can go either way. However, it's really important to just answer what's given and not go beyond and make assumptions.

But this is requiring me to assume I'm dealing with the lower temp range without explicity stating so, no?
I've had that problem as well of second-guessing and over-complicating some AAMC problems - how are you trying to fix that?

 

[ohkos1]

But this is requiring me to assume I'm dealing with the lower temp range without explicity stating so, no?
I've had that problem as well of second-guessing and over-complicating some AAMC problems - how are you trying to fix that?

I'm just trying to figure out what the AAMC wants us to know. Really read the explanations carefully to figure out what they want you to know. Tbh, I am still struggling quite hard with some of the questions that they ask. It can be really frustrating at times, because it's not really a content gap or an issue of needing to review more.

For example, yesterday I came up to this problem from one of the AAMC's that illustrates over thinking and over analyzing a question:

Embryonic mouse cells divide every 10 hours at 37 degrees Celsius. How many cells would be produced from an egg after three days?

a) less than 50
b) between 50 and 500
c) between 500 and 5000
d) greater than 5000

My thought process was: Hmm three days makes the egg a morula and morula should have 8-16 cells after 3 days... Wait, it says embryonic, which means it's a blastocyst which have a minimum of 128 cells. Are they assuming I know this? Do they want me to calculate from 128 as the initial number of cells? It turns out they just wanted me to use 1 cell as the base and the answer was b. As you can see, these type of questions are nightmares for me.

 

[erythrocyte666]

I'm just trying to figure out what the AAMC wants us to know. Really read the explanations carefully to figure out what they want you to know. Tbh, I am still struggling quite hard with some of the questions that they ask. It can be really frustrating at times, because it's not really a content gap or an issue of needing to review more.

For example, yesterday I came up to this problem from one of the AAMC's that illustrates over thinking and over analyzing a question:

Embryonic mouse cells divide every 10 hours at 37 degrees Celsius. How many cells would be produced from an egg after three days?

a) less than 50
b) between 50 and 500
c) between 500 and 5000
d) greater than 5000

My thought process was: Hmm three days makes the egg a morula and morula should have 8-16 cells after 3 days... Wait, it says embryonic, which means it's a blastocyst which have a minimum of 128 cells. Are they assuming I know this? Do they want me to calculate from 128 as the initial number of cells? It turns out they just wanted me to use 1 cell as the base and the answer was b. As you can see, these type of questions are nightmares for me.

We are twins in this aspect. It's so much MORE frustrating that my science mistakes are not from content but from this kind of overthinking that results from bringing in too much outside knowledge! I'd be much happier if it was just content errors that I can watch a video about.
That said, when I did the above problem the first half of the question stem did direct me to the 1(2^n) solution.

 

[amy_k]

I don't think it is a great question, it just seems to be specifically trying to catch out those who immediately see presence of cholesterol and relate it to fluidity. If nothing is mentioned about temperature, I would assume it is at "normal" temperature ranges.