I studied an BSc in genetics and none of our lectures or textbooks presented mitochondria any differently from the classic bean shape they introduce in school. This is surely old news to folks who specialise in mitochondria, but it's easy to miss out on these fundamentals even if you've studied in a relevant area at degree level, because there's just so much to know in biology.
In fact, it's one of those fields where the more you learn, the more you realise we'll never reach a satisfactory understanding in our lifetime. You could chuck an endless supply of PhD students at every constituent domain for generations and still feel like you've scarcely scratched the surface of the many things there are to question.
I'm reading an excellent book right now called Cells, Embryos and Evolution, in which one topic is the exploratory nature of certain biological processes. One of the processes described is the dynamic instability of microtubule growth.
Microtubules randomly grow and shrink from an anchor in the cell until they hit something that stabilizes them. Through their random growth they explore the cell, which means that processes depending on microtubules are robust against changes in size and shape of both the containing cell and the target object that needs the microtubules. The author explains that we still don't know how microtubules are stabilized, which I thought was fascinating.
Except that the book was written twenty years ago, and now we DO know how they are stabilized. It turns out that the author was the person who discovered microtubule instability, and since then we have not only figured out what stabilizes them, but have developed numerous cancer drugs based on those molecules: https://www.ncbi.nlm.nih.gov/books/NBK9932/#_A1831_
> You could chuck an endless supply of PhD students at every constituent domain for generations and still feel like you've scarcely scratched the surface of the many things there are to question.
Sounds like a much better use of tax dollars than some other uses!
Not in genetics, but the kind of cursory neuroscience education that "AI" courses contain often goes no further than a sample cell at one point in the first weeks. I have found that the majority of AI graduates believe each cell contains one Mitochondria, even those who can explain the chemical processes behind associative memory and understand how there are multiple binding sites/receptors in most of those processes.
It goes to show how much simple diagrams influence understanding. The synaptic gap diagrams show multiple receptors and abstracted neurotransmitters, and gradients of multiple Ca or K ions. The neuron diagram shows one Mitochondria. That start influences their understanding for years.
> This is surely old news to folks who specialise in mitochondria
from Wiktionary:
> mitochondrion, Coined in German by Carl Benda in 1898, from Ancient Greek μίτος (mítos, “thread”) + χονδρίον (khondríon), diminutive of χόνδρος (khóndros, “grain, morsel”)
from Wikipedia article on Carl Benda:
> In an 1898 experiment using crystal violet as a specific stain, Benda first became aware of the existence of hundreds of these tiny bodies in the cytoplasm of eukaryotic cells and assumed that they reinforced the cell structure. Because of their tendency to form long chains, he coined the name mitochondria ("thread granules").
So yeah, I guess this is known ever since mitochondria was first discovered, definitely "old news". I can't understand why it is always depicted as bean-shaped.
I have a BS in neurobiology from 2005 and the one lesson I took away and has been reinforced over and over again for me is that we know very little about biology. For example, epigenetics was only just getting talked about when I graduated. We are still only scratching the surface.
Mitochondria are a descendant of early bacteria which infiltrated an Archaea cell, traded genes, and started replicating with it, forming a new organism about 1.5bn years ago.
The wild part is that all mitochondria are descended from that single event.
This was a rather controversial theory called Endosymbiosis and it was pioneered by Lynn Margulis. Now it is widely accepted.
Because there was some skepticism in the thread about this theory, I emailed one of the top scholars in this area to get his up to date perspective and he delivered this amazing response:
"I'll be happy to give you a succinct summary of my views on this issue.
Molecular evidence (notably DNA sequence) absolutely confirms that the mitochondrial genome is of bacterial origin. The most compelling evidence in this regard comes from the sequence of the mitochondrial DNA (mtDNA) in a group of protists (eukaryotic, mostly single-celled, microbes) called jakobids. Key publications presenting the evidence and the arguments are:
Lang BF, Burger G, O'Kelly CJ, Cedergren R, Golding GB, Lemieux C, Sankoff D, Turmel M, Gray MW. 1997. An ancestral mitochondrial DNA resembling a eubacterial genome in miniature. Nature 387:493-497.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&d...
Burger G, Gray MW, Forget L, Lang BF. 2013. Strikingly bacteria-like and gene-rich mitochondrial genomes throughout jakobid protists. Genome Biol. Evol. 5:418-438.
http://gbe.oxfordjournals.org/content/5/2/418.abstract
While sequence data firmly support the endosymbiont hypothesis insofar as the mitochondrial genome is concerned, the data also support the conclusion that the mitochondrion originated only once:
Of course, only a few essential mitochondrial proteins are encoded in mtDNA and synthesized inside mitochondria. The vast majority of the 2000+ proteins that make up a mitochondrion are encoded in the nuclear genome, synthesized in the cytoplasm, and imported into mitochondria. So, when we speak about the origin of the mitochondrion, we have to account not only for the mitochondrial genome (which is unquestionably of bacterial origin) as well as the mitochondrial proteome: the collection of proteins that constitute the complete organelle.
Accepting that the mitochondrion originated as a captive bacterium or bacteria-like entity, massive evolutionary restructuring has evidently occurred in the transition from endosymbiont to integrated organelle, including endosymbiotic gene transfer (movement of genes from the endosymbiont genome to the nuclear genome, with loss of the mtDNA copies), recruitment of host proteins, and acquisition of new proteins from outside the host via lateral gene transfer from other organisms. A very complicated business, made even more complicated by the recognition that subsequent mitochondrial evolution has taken different pathways in certain respects in different eukaryotic lineages.
While the CONCEPT of the endosymbiont hypothesis, as outlined above, is strongly supported and accepted, HOW this might have happened is still unclear, and may never be settled to everyone's satisfaction. Did the mitochondrion emerge early in the evolution of the eukaryotic cell through the union, by an unspecified mechanism, of a primitive archaeon (host) and primitive bacterium (endosymbiont), with this union actually being instrumental in the emergence of the eukaryotic cell? Or, did the mitochondrion emerge late, in an evolving archaeon host that already had some of the hallmarks of a typical eukaryotic cell, notably phagocytosis, the well-known mechanism by which modern eukaryotic cells take up bacteria for food? The pros and cons of these two (and many other) scenarios are still being hotly debated.
Does anyone here have a sense of what time frame the video covers? Like, is that real-time and mitochondria are continuously mildly active? Is it vastly slowed down and mitochondria are ripping around in our cells like madmen? Is it vastly sped up and mitochondria are actually relatively static, slow movers?
Really sucks that antibiotics, especially bacteriocidal ones, appear to target mitochondria as if they were bacteria. This mistargetting causes sometimes severe and long-lasting side effects.
In the Halo universe, the "Hunter" enemy, the hulking shitheads covered in armor and blasting you with a fuel rod cannon and you have to shoot their orange weak spots, are actually colonies of little orange worms!
Also IIRC they work in pairs because they are mates. When you fight them you are killing a couple.
more like wiggly other cells, which are essential as one of our main energy systems. It's funny when you dig into these, the terms are things like fermentation[0]... say what? My body is producing beer for energy?
Even the Wikipedia entry on them has the classic bean-shaped diagram. If they are not really like that, why did that become the standard representation? Have they always been know to exist in more network-like structures, and was that why there was initial resistance to seeing their origin in free-living prokaryotes?
Cell diagrams are simplifications. Cells are not like your room with a few things inside. They are more like a decent city. In human cells you have hundreds to thousands of mitochondria.
It was because they could only image a dead/fixed 2D cross section on an electron microscope. The 2D cross section of a vast interconnected network of tubes looks like disconnected small “beans.”
Readit News
In fact, it's one of those fields where the more you learn, the more you realise we'll never reach a satisfactory understanding in our lifetime. You could chuck an endless supply of PhD students at every constituent domain for generations and still feel like you've scarcely scratched the surface of the many things there are to question.
Microtubules randomly grow and shrink from an anchor in the cell until they hit something that stabilizes them. Through their random growth they explore the cell, which means that processes depending on microtubules are robust against changes in size and shape of both the containing cell and the target object that needs the microtubules. The author explains that we still don't know how microtubules are stabilized, which I thought was fascinating.
Except that the book was written twenty years ago, and now we DO know how they are stabilized. It turns out that the author was the person who discovered microtubule instability, and since then we have not only figured out what stabilizes them, but have developed numerous cancer drugs based on those molecules: https://www.ncbi.nlm.nih.gov/books/NBK9932/#_A1831_
The progress of science is really incredible.
Sounds like a much better use of tax dollars than some other uses!
It goes to show how much simple diagrams influence understanding. The synaptic gap diagrams show multiple receptors and abstracted neurotransmitters, and gradients of multiple Ca or K ions. The neuron diagram shows one Mitochondria. That start influences their understanding for years.
from Wiktionary:
> mitochondrion, Coined in German by Carl Benda in 1898, from Ancient Greek μίτος (mítos, “thread”) + χονδρίον (khondríon), diminutive of χόνδρος (khóndros, “grain, morsel”)
from Wikipedia article on Carl Benda:
> In an 1898 experiment using crystal violet as a specific stain, Benda first became aware of the existence of hundreds of these tiny bodies in the cytoplasm of eukaryotic cells and assumed that they reinforced the cell structure. Because of their tendency to form long chains, he coined the name mitochondria ("thread granules").
So yeah, I guess this is known ever since mitochondria was first discovered, definitely "old news". I can't understand why it is always depicted as bean-shaped.
Do you disagree with the reason suggested in the article?
Depends on how long you intend to live, really
https://slatestarcodex.com/2017/11/09/ars-longa-vita-brevis/
The wild part is that all mitochondria are descended from that single event.
This was a rather controversial theory called Endosymbiosis and it was pioneered by Lynn Margulis. Now it is widely accepted.
https://evolution.berkeley.edu/it-takes-teamwork-how-endosym...
"I'll be happy to give you a succinct summary of my views on this issue.
Molecular evidence (notably DNA sequence) absolutely confirms that the mitochondrial genome is of bacterial origin. The most compelling evidence in this regard comes from the sequence of the mitochondrial DNA (mtDNA) in a group of protists (eukaryotic, mostly single-celled, microbes) called jakobids. Key publications presenting the evidence and the arguments are:
Lang BF, Burger G, O'Kelly CJ, Cedergren R, Golding GB, Lemieux C, Sankoff D, Turmel M, Gray MW. 1997. An ancestral mitochondrial DNA resembling a eubacterial genome in miniature. Nature 387:493-497. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&d...
Burger G, Gray MW, Forget L, Lang BF. 2013. Strikingly bacteria-like and gene-rich mitochondrial genomes throughout jakobid protists. Genome Biol. Evol. 5:418-438. http://gbe.oxfordjournals.org/content/5/2/418.abstract
While sequence data firmly support the endosymbiont hypothesis insofar as the mitochondrial genome is concerned, the data also support the conclusion that the mitochondrion originated only once:
Gray MW, Burger G, Lang BF. 1999. Mitochondrial evolution. Science 283:1476-1481. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&d...
Of course, only a few essential mitochondrial proteins are encoded in mtDNA and synthesized inside mitochondria. The vast majority of the 2000+ proteins that make up a mitochondrion are encoded in the nuclear genome, synthesized in the cytoplasm, and imported into mitochondria. So, when we speak about the origin of the mitochondrion, we have to account not only for the mitochondrial genome (which is unquestionably of bacterial origin) as well as the mitochondrial proteome: the collection of proteins that constitute the complete organelle.
Accepting that the mitochondrion originated as a captive bacterium or bacteria-like entity, massive evolutionary restructuring has evidently occurred in the transition from endosymbiont to integrated organelle, including endosymbiotic gene transfer (movement of genes from the endosymbiont genome to the nuclear genome, with loss of the mtDNA copies), recruitment of host proteins, and acquisition of new proteins from outside the host via lateral gene transfer from other organisms. A very complicated business, made even more complicated by the recognition that subsequent mitochondrial evolution has taken different pathways in certain respects in different eukaryotic lineages.
While the CONCEPT of the endosymbiont hypothesis, as outlined above, is strongly supported and accepted, HOW this might have happened is still unclear, and may never be settled to everyone's satisfaction. Did the mitochondrion emerge early in the evolution of the eukaryotic cell through the union, by an unspecified mechanism, of a primitive archaeon (host) and primitive bacterium (endosymbiont), with this union actually being instrumental in the emergence of the eukaryotic cell? Or, did the mitochondrion emerge late, in an evolving archaeon host that already had some of the hallmarks of a typical eukaryotic cell, notably phagocytosis, the well-known mechanism by which modern eukaryotic cells take up bacteria for food? The pros and cons of these two (and many other) scenarios are still being hotly debated.
Hope this helps.
Cheers,
Michael W. Gray, PhD, LLD (h.c.), FRSC
Professor Emeritus
Department of Biochemistry and Molecular Biology
Dalhousie University
Halifax, Nova Scotia B3H 4R2, Canada."
Dead Comment
https://x.com/mag2art/status/1385940103189745669
Deleted Comment
HP would be absolutely thrilled to know that. Or maybe terrified out of his mind. One of the two for sure.
Also IIRC they work in pairs because they are mates. When you fight them you are killing a couple.
[0] https://en.wikipedia.org/wiki/Fermentation