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NBME 20 Answers

nbme20/Block 3/Question#19 (34.4 difficulty score)
A 23-year-old man comes to the physician ...
Area labeled ‘B’ (Mitochondrion)🔍

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submitted by usmle11a(70),
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gusy sthi divoe xeiaslnp otla

submitted by jinzo(13),

A - nucleus ( with nucleolus inside ) B - mitochondria C - RER ( you can see attached ribosomes ) D - ?? may be lysosomes E - glycogen granules

weenathon  I don't think A is the nucleus, It seems more like a lysosome with digested material inside. If you watch the video below it shows the relative size of the nucleus to the mitochondria - a nucleus would be MUCH bigger than the mitochondria +5  
weenathon There are very similar looking pictures in this article, it must be a peroxisome +1  

submitted by lianallado(2),
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submitted by qfever(29),

Does anyone know what are A, C, D? For C not sure if it's pointing to the ribosomes on RER.

(I'm assuming E is glycogen granules based on a comment below!)

drdoom  see @jinzo’s comment above +  

submitted by usmile1(86),
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esod yonena onwk tawh eth sctrutrue E si nnigtpoi ot?

thomasburton  Not sure looks like it might be free ribosomes or other such small cytosolic structure (I picked E too, thought B looked way too big!) +  
targetusmle  same here!! marked e thinking of it as a mitochondria +1  
msyrett  Glycogen Granules! They are not membrane bound and float freely in the cytoplasm. +1  

submitted by hombremasorca(0),

Anyone find a problem with the stem? Seems to me that it doesn't help to state "however, his father's sister and children are unaffected". We already know the mutation runs in the mother's side, right? It seems like that statement doesn't discard nor confirm any inheritance pattern. Why would we care about the patient's father's side?

bbr  It just further helps to tell us this is mitochondrial. I guess they are doing us a favor. +