Questions regarding organelles and cellular evolution

[marshmallow]

I’m sure I’m still considered a greenhorn when it comes to biology in general. Most of my education so far has focused on genetics, transcription, and a detailed overview of the cell’s machinery and their function. I wish to plug some holes that I’m curious about.

1. All discussions of meiosis/mitosis have had an almost tunnel vision effect on the genome, which is understandable since that’s the main point of reproduction. But what about the organelles? I know that mitochondria and plastids undergo fission but what about all the other myriad organelles?

The closest I found to an answer was here

All of the other cellular organelles are reproduced by the nuclear genome. During cell division, the existing organelles are divided fairly equally between the 2 daughter cells. Then any additional organelles that the daughter cells require, such as ribosomes, are assembled from nuclear gene products, such as rRNA & proteins in the case of ribosomes. The process is almost identical to that which replenishes mitochondria and chloroplasts in the daughter cells, except that it is directed by the nuclear genome, since these other organelles do not have their own DNA, as you correctly noted.

This didn’t help. Is he saying that material buds off from the nucleus and transforms into said organelles? What about the membranes that enclose many of them? I’m having great difficulty visualizing this process. It seems to me that the mass of all the organelles put together is pretty significant when compared to the entire cell and a lot of extra nutrients would be needed (or am I wrong on that point?).

Or is he saying that each organelle splits in a mini-mitosis/fission fashion and then grows later? I would be curious how that works.

2. The widely accepted view is that mitochondria and plastids are ancient bacteria symbiots for the common ancestor of all eukaryotes, which seems to fit the evidence (e.g. their own circular dna/rna, mini-organelles, undergoes fission, etc.). What about the organelles? They seem like very complex pieces of machinery; are there any models of where they came from and how long it took; possibly in some order? One at a time? All at once?

3. Can mitochondria or plastids live outside of a cell or are they so specialized and dependant on the cell that it would be a sure death?

[Nunavut_Boy]

I think what he’s saying is that the EXISTING organelles in the parent cell are divided equally between the daughter cells. Ex. Original cell has 10 mitochondria, each daughter cell will have 5.

After that, any needed organelles are synthesized within each daughter cell.

[Nunavut_Boy]

As for 3), is a mitochondrion ‘alive’? I don’t think it is considered to be alive even though it has it’s own RNA. They say it came from some ancient, symbiotic life but now it has changed so much so that it is not considered ‘alive’ on its own. Therefore a lone mitochondrion outside of a cell is just a piece of cellular machinery outside of a cell.

If what you are asking is whether or not a mitochondrion can continue to process the same biochemical reactions that it would if it were still inside the cell, I would think not. Don’t they rely on other organelles to provide them with ‘seed materials’ to begin said reactions? I don’t remember as much abou this as I should.

I’m sure someone more knowledgable will be along shortly to rectify whatever errors I have made.