NBME 20 Area labeled ‘B’ (Mitochondrion) (NBME Answers)

Retired NBME 20 Answers

nbme20/Block 3/Question#19 (reveal difficulty score)
A 23-year-old man comes to the physician ...
Area labeled ‘B’ (Mitochondrion) 🔍 / 📺 / 🌳 / 📖
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+17 upvote downvote
submitted by ∗usmle11a(102)

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https://www.youtube.com/watch?v=k0YqEpA-62A

guys this video explains alot

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+8 upvote downvote
submitted by jinzo(15)

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

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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 +7

weenathon https://www.ncbi.nlm.nih.gov/books/NBK26858/ There are very similar looking pictures in this article, it must be a peroxisome +5

+2 upvote downvote
submitted by lianallado(3)

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This patient presents with a mitochondrial myopathy since the disorder is inherited from the mother. Mitochondrial myopathies show “ragged red fibers” on muscle biopsy due to the accumulation of diseased mitochondria in the subsarcolemma of the muscle fiber.

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+1 upvote downvote
submitted by ∗qfever(67)

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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!)

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drdoom see @jinzo’s comment above +

+1 upvote downvote
submitted by ∗usmile1(154)

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does anyone know what the structure E is pointing to?

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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. +4

+0 upvote downvote
submitted by hombremasorca(0)

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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?

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

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