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Mitochondria Are Alive

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Re: Mitochondria Are Alive

#101

Post by andrewla »

dekhn wrote: post #83
andrewla wrote: post #54

I read the article waiting for an answer to the question "in what operational sense does this matter?" but it never arrived. The question posed is whether we consider mitochondria to be "alive". It's just a word, who cares. What do we do differently given this assumption?

It matters for a number of reasons, but the main reason in terms of pure biology is that it was not originally recognized that cells could absorb other cells and utilize them for the absorbed cell's natural function. This meant, importantly, that we learned cells did not always need to evolve a functionality from scratch, but could acquire it through phagocytosis. It's also a useful tool for studying evolution for ma…

Whether or not mitochondria were once viable independent organisms that were absorbed by early eukaryotes does not depend on whether we call their modern descendants "living" or not. If we determine that they did, then we still don't have to call them alive -- certainly things like mitosomes exist and are suspected to have either evolved from mitochondria or evolved after amitochondrial division, but do not have DNA and do not reproduce independently but fulfil similar functions.

We know they have DNA, we know they reproduce independently of the host cell, we know to a degree why they tend to move to both sides on cell division. We know lots of stuff about them and we can always learn lots more. Whether they are "alive" or not has absolutely no bearing on that, other than to naval-gaze.

Re: Mitochondria Are Alive

#102

Post by dekhn »

andrewla wrote: post #101
dekhn wrote: post #83

Earlier quoted context omitted.

It matters for a number of reasons, but the main reason in terms of pure biology is that it was not originally recognized that cells could absorb other cells and utilize them for the absorbed cell's natural function. This meant, importantly, that we learned cells did not always need to evolve a functionality from scratch, but could acquire it through phagocytosis. It's also a useful tool for studying evolution for ma…

Whether or not mitochondria were once viable independent organisms that were absorbed by early eukaryotes does not depend on whether we call their modern descendants "living" or not. If we determine that they did, then we still don't have to call them alive -- certainly things like mitosomes exist and are suspected to have either evolved from mitochondria or evolved after amitochondrial division, but do not have DNA…

Oh, I see, you're getting hung up on the use of the term alive for modern mitochondria.

This sort of definitional argument is not interesting to me.

Re: Mitochondria Are Alive

#103

Post by hurpdurpdurp »

JumpCrisscross wrote: post #78

Mitochondria are why I’m a Rare Earther. In Earth’s history, mitochondrial endosymbiosis occurred once. Without that you don’t have the energy budget for complex life. Moreover, there may be a narrow window where it can happen: modern microbiology has defences and selection pressures that it make inhospitable to the hobbling chimeræ the first mitochondrial cells would have been. Until mitochondria, the emergence of l…

I know nothing about biology, pardon my ignorance. From the article it sounds like mitochondria were a separate organism that has perhaps simplified through specialization and is currently on the boundary of being an independent life form. It also sounds like there are other structures (golgi apparatus are mentioned?) which are not on the bubble. Are we sure that there is not an arrow of time here, where once those other structures were also semi-independent and have become less so?

More broadly, it leads me to wonder whether cellular life might eventually/might have at some point specialize towards hosting novel endosymbioses.

Either scenario, assuming what I'm saying isn't just total nonsense, would seem to make the state of mitochondria less of a one-off event and more of the instance of that event we are around at the right time to observe.

Re: Mitochondria Are Alive

#104

Post by davideg »

andrewla wrote: post #88
davideg wrote: post #82

Earlier quoted context omitted.

> Defining mitochondria as “nonliving” isn’t just a classification mistake, nor a question of word choice. Rather, it is a fundamental misunderstanding of the nature and role of mitochondria. It inherently undermines our understanding of biological systems and deeply influences the tools we build to study them. Once you accept mitochondria as alive, you might be motivated to explore its "potential" niche, as describe…

So the theory is that if we don't accept them as alive, then we can't experiment with implanting cross-species mitochondria in human cells? Why not? What stops us from doing this?

This is a fair point. I can see the excitement around recognizing that mitochondria is alive to motivate exploring its other functions. But I think you're right someone might be interested in that exploration regardless of whether it's considered alive.

Edit: to your point, there are plenty of scientists interested in studying viruses and much debate about whether or not they are alive. Ultimately it probably doesn't matter.

I do think when you consider mitochondria to be alive, it broadens the scope of your thinking because you start considering each characteristic of life in relation to mitochondria. You might not be motivated to do that without thinking in those terms.

Re: Mitochondria Are Alive

#105

Post by andrewla »

dekhn wrote: post #102
andrewla wrote: post #101

Earlier quoted context omitted.

Whether or not mitochondria were once viable independent organisms that were absorbed by early eukaryotes does not depend on whether we call their modern descendants "living" or not. If we determine that they did, then we still don't have to call them alive -- certainly things like mitosomes exist and are suspected to have either evolved from mitochondria or evolved after amitochondrial division, but do not have DNA…

Oh, I see, you're getting hung up on the use of the term alive for modern mitochondria. This sort of definitional argument is not interesting to me.

I think we're in agreement then -- this article is not about "did mitochondria evolve from absorbed viable organisms as opposed to evolving directly", which is an interesting question that impacts our understanding of evolution in microbiology. The article is about whether "Microchondria Are Alive" which is a useless naval-gaze.

Re: Mitochondria Are Alive

#106

Post by dekhn »

andrewla wrote: post #84
The_Colonel wrote: post #73

Earlier quoted context omitted.

That seems to be an overly reductive view on the value of knowledge. What practical purpose does studying ancient civilizations have? Why do we send expensive telescopes into space to study faraway galaxies and try to uncover mysteries of the big bang? When can we expect the results from number theory to lower the price of gas at the pump?

But the definition of a word is not knowledge. Knowing that mitochondria have their own DNA is knowledge. Knowing that they reproduce independently of their home cell is knowledge. Learning whether they evolved from a separate viable organism would be knowledge. Learning whether we can make them viable, or breed them separately, and use them in therapies -- all knowledge. Whether they are "alive" or not is just the d…

Much of science is about defining words in ways that match the underlying general structure of the system being studied.

A subset of scientists want to come up with an operational definition of "What is life", which may or may not include things like viruses and mitochondria. As you say, it's mostly definitional, but by defining this, we can potentially make our understanding match up with the latent reality.

Re: Mitochondria Are Alive

#107

Post by pishpash »

twothreeone wrote: post #46
adastra22 wrote: post #37

Earlier quoted context omitted.

Organelles are alive too. All active biological systems are alive. Mitochondria have for many generations now been known to have their own DNA and replicate on their own. So I’m not sure what new distinction is being drawn?

I _think_ what they mean is it's not typically listed as a "life form" in its own right, i.e., there's no Domain under which one would classify Mitochondria - maybe just calling them bacteria would capture the article's intent? So, the modification would be that we are living in symbiosis with mitochondrial bacteria, similar to how we live in symbiosis with our gut bacteria, rather than them being classified as "orga…

Of course it is classified. In Wikipedia itself there is a phylogenetic tree listing its closest relative the alphaproteobacteria: https://en.wikipedia.org/wiki/Mitochondrion#Origin_and_evolu...

Re: Mitochondria Are Alive

#108

Post by hammock »

nemonemo wrote: post #76
andrewla wrote: post #54

I read the article waiting for an answer to the question "in what operational sense does this matter?" but it never arrived. The question posed is whether we consider mitochondria to be "alive". It's just a word, who cares. What do we do differently given this assumption?

It doesn't seem the article addresses this, but I'd ask these questions: "would it be possible that mitochondria's evolutional interest and the organism's interest are not aligned?" "how many independent DNA can an organism possess?" "why mitochondria do not elicit immune reactions? Or can they?"

1) https://en.wikipedia.org/wiki/Mother%27s_curse

2) By "organism" I assume you mean "cell" since humans have several thousand different species with their own DNA living on or inside the body at any given moment. We can speak of animal cells, which have two (species and mitochondria) - and plant cells, which have three (species, mitochondria, and chloroplasts). If there can be one two or three, I don't see why there couldn't be even more.

3) Mitochondria are usually sequestered within the cell, which limits their exposure to immune cells. The immune system primarily targets pathogens that are outside the host cells. In fact, some pathogens can exploit mitochondrial pathways to evade immune detection - the most famous of which is HIV.

Re: Mitochondria Are Alive

#109

Post by devilbunny »

piombisallow wrote: post #98
jamiek88 wrote: post #77

Earlier quoted context omitted.

Excellent point. Are there mitochondria in neurons?

Every cell in the body (except blood cells) has mithocondria.

Nitpick: except red blood cells. White cells very much do have mitochondria.

RBC's don't need them because they are incredibly low-metabolism. It's energetically cheaper for the organism just to make them, let them go for a few months, and then recycle the components.

Re: Mitochondria Are Alive

#110

Post by dekhn »

andrewla wrote: post #105
dekhn wrote: post #102

Earlier quoted context omitted.

Oh, I see, you're getting hung up on the use of the term alive for modern mitochondria. This sort of definitional argument is not interesting to me.

I think we're in agreement then -- this article is not about "did mitochondria evolve from absorbed viable organisms as opposed to evolving directly", which is an interesting question that impacts our understanding of evolution in microbiology. The article is about whether "Microchondria Are Alive" which is a useless naval-gaze.

I dunno if I agree it's a total navel gaze.

For example I could easily see a scientist asking the question, "if mitochrondira are not alive, at which point did the phagocytosis of the initial prokaryotic cell lead to the mitochondria not being alive?" "What components were lost in the cell that lead to the loss of life?" I agree these aren't particularly useful, and are ultimately definitional, but definitions matter a lot in science, especially when paradigms change.

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