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Why arent mitochondria identified as food bythe cell its in?

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Why arent mitochondria identified as food bythe cell its in?

Postby RagingLiberal » Thu Nov 26, 2009 2:15 am

Why aren't mitochondria/chloroplasts identified as foreign objects / food by the cell that it resides in?
I know this endosymbiotic relationship benefits both the cell and the organelle, and if the cell starts attacking the mitochondria/chloroplast, the cell might as well commit suicide, but what is stopping the cell from identifying the organelle as a foreign object / food?
It doesn't have to be the "correct" answer, I just want to know a plausible explanation.

And, to clear things up:
Not just immune cells, all cells. Why don't they ingest their own mitochondria/chloroplasts.

I tried asking this in Yahoo Answers, but she didn't actually answer the question. Yes, I know mitochondria are considered organelles by the cell, but how? "Identification" proteins made by the mito/chlor?
http://answers.yahoo.com/question/index ... 723AANsXzt

No, I'm not a creationist.
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Postby biohazard » Thu Nov 26, 2009 9:31 am

Basically all such cellular level recognition events are based on molecules recognizing specific molecular structures (often receptor-mediated or enzyme+ligand). Cells do not degrade their own mitochondria / chloroplasts mostly because in normal conditions they lack enzymes that would be specific for the surface molecules of those organelles, which is a requirement for breaking down the organelle.

Phagocytes (especially macrophages) have receptors that recognize small "objects" in their vicinity, but since these receptors are on the cell surface, its own mitochondria do not get phagocytosed and degraded. Free mitochondria outside the macrophage do get "eaten", because the cell transports them to its lysosomes where are enzymes and compounds that degrade other cells and/or their organelles.
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Re: Why arent mitochondria identified as food bythe cell its in?

Postby RagingLiberal » Thu Nov 26, 2009 9:49 am

Cool.
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