Sizes at the cellular level

[reising1]

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I personally find this to be really ridiculous that we should know, but I wanted to see what everyone else thought. I can't imagine going back and trying to study all the sizes of all the different major microscopic components on the MCAT.

Here's a question from a practice test. It tells you that something is 100 nanometers in diameter.

Q: In regard to their relative size, the described objects are
A. smaller than all known eukaryotic cells
B. approximately the size of a typical coccus bacterium
C. larger than a human red blood cell corpuscle
D. larger than all known bacteriophages
Answer: A

I mean...really? We really ought to be able to answer questions like this?

 

[secretsunset29]

I think it's a reasonable question. The differences between each of the 4 answer choices is at least a 10-fold increase in diameter.

100 nm is VERY small
Eukaryotic cells are about 1-100 um (safest answer)
Coccus bacterium are about 0.1-1.0 um (larger than 100 nm)
RBC is about 6-8 um (way bigger than 100nm)
ALL bacteriophages (too general of an answer)

Hope this helps

 

[reising1]

But did you really know those numbers off the top of your head? I mean, you can't even find those values in any review book.

 

[mcloaf]

This is way easier than you're making it. You don't need to know the precise sizes of all those things to know that 100 nm is way smaller than a eukaryotic cell, and this IS something you should know.

 

[reising1]

So we should know the size of eukaryotic cells?

 

[TSSVR4]

If I recall this specific passage indirectly told you it was a virus. That should give you the answer.

 

[reising1]

If I recall this specific passage indirectly told you it was a virus. That should give you the answer.

It told you it was a virion. Does this mean it's the smallest possible one?

 

[ToldYouSo]

Think of it this way:

Eukaryote: micrometer range (10^-6)
Virus: nanometer range (10^-9)

 

[TSSVR4]

It told you it was a virion. Does this mean it's the smallest possible one?

Yep, except bacteriophages which can be smaller

 

[ZezKaiEll]

This question could be tough if you don't have a relative knowledge of the sizes of cells. I do think I recall a mention of this in the PR bio review though.

If you didn't know this though, perhaps you could use the fairly imprecise way of estimating based on the size of DNA. The width of DNA is measured in Angstroms; even with it wrapped in chromosomes you get an idea for how small this amount is compared to diagrams of a cell and nucleus within it which you have no doubt seen. Maybe through this you could estimate that the diameter of a eukaryotic cell is far bigger than 100 nm (1000 angstroms). Even though there is variation in sizes of Eukaryotic cells I don't think one could be that much smaller than the others.

 

[catinthehat1234]

I personally find this to be really ridiculous that we should know, but I wanted to see what everyone else thought. I can't imagine going back and trying to study all the sizes of all the different major microscopic components on the MCAT.

Here's a question from a practice test. It tells you that something is 100 nanometers in diameter.

Q: In regard to their relative size, the described objects are
A. smaller than all known eukaryotic cells
B. approximately the size of a typical coccus bacterium
C. larger than a human red blood cell corpuscle
D. larger than all known bacteriophages
Answer: A

I mean...really? We really ought to be able to answer questions like this?

I'm just doing this question now, and I feel you. But it's good to know someone else felt the way I did a few years ago too haha 🙂