Theoretically, mitochondria are said to be a separate organism that is concerned with its own life and its own processes. In fact, it even duplicates individually. I know a similar question is here but I have something else apart from that to ask.

  1. Is the presence of their own DNA/RNA - like compound justify or prove that the mitochondria was once a separate living organism?
  2. If the mitochondria is indeed a separate living organism, then how is it controlled by the nucleus? Or is it not? Logic would suggest that since mRNA exists in the mitochondria separate from DNA in the nucleus, they have their own control over how they behave.
  3. Often, living organisms working together have to have some sort of payment system. For example, bacteria in the body provide Vitamin K and other breakdown vitamins, and in return the body gives it a suitable home to live in. Is there any such business occurring between the individual cell and the mitochondria? Does it keep some nutrients for itself? If not, what is its mode of nutrition?
  4. In effect, cells did exist before mitochondria joined the party. Is there any way to at least have a feasible hypothesis on why and how the cells bonded with the mitochondria or how the cells even existed in the first place without the presence of and organnelle that can break down food and convert it into energy?
  5. Why do mitochondria have their own membrane? And that too folded? Is that to increase the surface area available for the electron transport chain, or is it for simple compactness?
  6. Why does the mRNA in our bodies always exactly match the mRNA of our mothers and only our mothers? Can any genetic mutation change this fact?
  7. Is it possible, that a mitochondrion can somehow escape the cell and start performing its life otherwise?
  8. mRNA would suggest that mitochondria make their own proteins / at least some basic amino acids. If there are any such proteins, are they utilized for the cell? Or are they used for cellular respiration? Or are they kept by the mitochondria for there own means?

I will appreciate all answers!, SmallDeveloper (a.k.a SmallScientist :) )

EDIT : Basically, I am asking 3 things:

  1. Were mitochondria really separate organisms once?
  2. If so, how do they get their nutrition?
  3. How did cells exist before mitochondria came along?
  • 1
    $\begingroup$ Have you read the Wikipedia article on the Endosymbiont theory? $\endgroup$
    – Chris
    Aug 14 '14 at 13:24
  • 2
    $\begingroup$ As @Chris pointed out, this is a very broad set of questions on mitochondrial endosymbiosis, and doesn't seem to show much in the way of independent research/effort into the question (not that you necessarily haven't). After doing some reading on endosymbiosis, come back and ask more specific questions (probably split up your list) on specific elements you are having trouble with. There are books dedicated to answering 1-8. $\endgroup$
    – Atl LED
    Aug 14 '14 at 14:52
  • $\begingroup$ Thanks for pointing that out. I have edited the question for a more minimalistic point but have kept the original question for reference. @Chris, yes, but then this does not explain how mitochondria get their nutrition now, neither how cells existed without them. I know its an unknown topic, I just wanted some hypotheses. $\endgroup$
    – user8269
    Aug 15 '14 at 13:20
  1. Yes. But it is incorrect to call mitochondria an organism now.
  2. Most of their genes were lost and are now encoded in the nuclear genome
  3. It gets most of its metabolites
  4. It is not known. See the other post for details.
  5. Why membrane: I guess you know that. Why folded: you guessed right.
  6. Only ovum donates mitochondria and other cytoplasmic factors. Sperm just provides the haploid genome.
  7. No
  8. Most of them are key respiratory enzymes
  • $\begingroup$ Thanks for the answer. Even though I asked I broad question, I didn't expect any broad answers. Really thanks for the prompt answer. $\endgroup$
    – user8269
    Aug 15 '14 at 7:39
  • $\begingroup$ About question 4, isn't endocytosis how mitochondria were adquired by primitive eukaryotes? I think that this notion is supported from the observation that some species today can establish symbiosis by ingesting other cells, such as Paramecium bursaria, which has Zoochlorella algae (another eukaryote) living inside. $\endgroup$
    – user38945
    Nov 27 '18 at 16:29
  • $\begingroup$ @Jagoe Question 4 is more than how organelles were acquired. Endocytosis is the first step. $\endgroup$
    Nov 27 '18 at 16:31
  • $\begingroup$ Then, I cannot provide more details. $\endgroup$
    – user38945
    Nov 27 '18 at 16:35