Find the odd one out and state the category of the rest.

  • Chloroplast
  • Mitochondria
  • Nucleus
  • Grana

Now my answers are :

  • 1st possibility : grana

    • Category : presence of DNA in others
  • 2nd possibility : grana

    • Category : all others are cell organelles

Are their any more possibilities and are my answers reasonably correct?

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    $\begingroup$ hmmm, that is difficult to know what to answer - it's probably possible to find criteria where each can be considered an odd one out! what was the context? (e.g. was it a practice exam for a module/course on DNA?) $\endgroup$ – rg255 May 31 '16 at 13:50
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    $\begingroup$ It was basically a worksheet on photosynthesis but i don't believe it is necessary to stick to the topic while answering, is it ? $\endgroup$ – user23312 May 31 '16 at 14:02
  • $\begingroup$ well if your exam is on photosynthesis it is a good clue to think about the differences in that context, rather than e.g. which ones contain nucleic acids $\endgroup$ – rg255 May 31 '16 at 14:10
  • $\begingroup$ But then there's no involvement of mitochondria in Photosynthesis right? @rg255 $\endgroup$ – user23312 May 31 '16 at 14:11
  • $\begingroup$ You're asking two questions at once here. Why not simplify it? I hope you don't mind, but I used this question as an example in meta to talk about how MCQs introduce several questions at once and would be better asked one part at a time. $\endgroup$ – James Jun 2 '16 at 7:28

I would say Nucleus is the odd one out. Chloroplast (which have Grana in them) and Mitochondria are involved in the process of creating/breaking down energy, whereas the Nucleus is, so to speak, the blue-prints of the cell.

To summarize:

Chloroplast is involved in Photosynthesis to create energy

Grana are in the Chloroplast, which is involved in Photosynthesis

Mitochondria are "the powerhouse of the cell" and help break down energy (ATP > ADP)

Nucleus is the cell's blue-prints

Therefore, it seems that the Nucleus is the least like the others.

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  • $\begingroup$ I would also go with Nucleus $\endgroup$ – Failed Scientist May 31 '16 at 13:47
  • $\begingroup$ Are my answers correct ? $\endgroup$ – user23312 May 31 '16 at 14:01
  • $\begingroup$ Technically, yes, your way of differentiating the Grana from the others is legitimate. However, I find that the Nucleus is more different from the others than the Grana is. Also, although Nucleus, Mitochondria and Chloroplast all have DNA, they are not all the same. Nucleus has DNA whereas Chloroplasts have ctDNA/cpDNA and Mitochondria has mtDNA. This is probably because there is a chance that both were organisms of their own, ages ago. learn.genetics.utah.edu/content/cells/organelles $\endgroup$ – XaNaX May 31 '16 at 14:08
  • $\begingroup$ But your answer doesn't mention the category of the rest as i asked $\endgroup$ – user23312 May 31 '16 at 19:16
  • $\begingroup$ You are looking for an answer of Grana that includes a third reason that Grana is the answer? Please try to be more clear. I believe what you want to know, (ei the similarity between the Chloroplast, Mitochondria and Grana) is that they are all used in the process or created and/or breaking down energy. $\endgroup$ – XaNaX May 31 '16 at 19:25

I think it should be grana..
Reasons- 1. It is not a cell organelle 2. It is not having double membrane 3. It does not have its own dna or ribosomes...

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Your answers are correct, but there are more to consider:

  • Nucleus is odd because it's the only one not directly involved in cell metabolism and has nothing to do with endosymbionts. Most cells also only have one nucleus but multiple mitochondria and chloroplasts - and multiple grana per chloroplast.
  • Granum is odd because it's neither a eukaryotic cell organelle nor double-membrane-bound. As Felix_17 mentions, it also contains neither DNA nor ribosomes.

It's hard to argue for mitochondria or chloroplasts to be the odd one out because both share a lot of properties (endosymbionts, importance for cell metabolism, properties deriving from their bacterial origin), and their differences aren't shared with nuclei and grana.

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