My biology is a bit rusty but I really have to wonder — are plants and animal cells even “alive”?

Take away the mitochondria and bacteria… can cells live on their own?

If no, then are we that all that different than this microbe?

Might even be sheer arrogance to think that we are the “host” (much like cats/dogs domesticating humans). Maybe we only exist to serve the mitochondria (:->

There are a few weird cases of prokaryotes that don't have mitocondrias. Apparently they had mitocondrias, but they steeled the interesting parts and get rid of them (over gazillions of years). From https://en.wikipedia.org/wiki/Metamonad

> These flagellates are unusual in lacking aerobic mitochondria. Originally they were considered among the most primitive eukaryotes, diverging from the others before mitochondria appeared. However, they are now known to have lost aerobic mitochondria secondarily, and retain both organelles and nuclear genes derived ultimately from the mitochondrial endosymbiont genome. Mitochondrial relics include hydrogenosomes, which produce hydrogen (and make ATP), and small structures called mitosomes.

I think I first came across this on HN: A Symbiotic View of Life: We Have Never Been Individuals [0]

[0]https://www.journals.uchicago.edu/doi/10.1086/668166

> Take away the mitochondria and bacteria… can cells live on their own?

We can live without bateria if we add with some food supplements.

mitochondria isn't considered alive, as a separate organism, AFAIK. It doesn't even have a species name. It's just a component of the host cell.

As I understand it, these new microorganisms are parasites. They're not essential for the functioning of the host cell like mitochondria are.

You were a single animal cell at some point. Seems to me that it must have been alive.

Essentially nothing can live on its own, certainly not animals.

> Take away the mitochondria [...] can cells live on their own?

Neither can live without the other. Too much genetic exchange has taken place in some distant ancestor where critical genes were deleted from mitochondria and moved to the host. Meanwhile host cells became utterly dependent on mitochondria for energy production. Or you might say: the mitochondria were producing so much excess ATP the host cells started evolving to depend on that much energy being available.

The exceptions are later cases (like a few organisms that have copied energy production from the mitochondria genome then later lost the mitochondria entirely).

For all purposes mitochondria are zombie archaea (not bacteria). Hollowed out empty shells retaining just enough function to perform aerobic respiration and reproduce. There is little pressure to evolve away from this local maxima. What benefit would the host cells derive from getting rid of the mitochondria? Not much. And having those critical functions isolated in what amounts to a pseudo-organelle with its own DNA protects it from a lot of sources of damage/error.

So... are we obligate symbiotes? Or have mitochondria hyper-evolved to such a point they are just organelles in our cells - just ones that carry their own DNA instead of relying on the cell's main DNA? Like much of biology... a bit of both in a fuzzy mix without a clear line.

When you say "take away the mitochondria," do you mean a prokaryote?

Mitochondria can't live without their surrounding cells. Plants are also interdependent with fungi.

Multicellular life is difficult without mitochondria. Personally I think that is the great filter.

"it takes a planet to make life"