38

SolarLunix posted an excellent answer detailing the criteria for being classified as "alive", and showed that by those criteria, mitochondria could be considered as "dead". However, I would argue that the narrator's statement in your video does not make any sense. The currently-accepted theory of the evolution of mitochondria (and possibly other organelles) ...


25

Isn't there a possibility that cell division will result in a daughter cell with no mitochondria? Yes, there is always the possibility. However, there must be a strong negative selection pressure against eukaryotic life that cannot achieve the proper partitioning of mitochondria, so you can imagine that there are mechanisms in place to prevent this case. ...


19

According to "Resolution of distinct rotational substeps by submillisecond kinetic analysis of F1-ATPase" (Yasuda et al., Nature, 2001), ATPase rotates at 130 revolutions per second when saturated with ATP.


19

Mitochondria evolved before chloroplasts. We know this because Mitochondria form a monophyletic group: e.g. all life with mitochondria traces back to a single common ancestor (source). Since the group with chloroplasts groups within this clade, it must be the case that either (a) chloroplasts were obtained by an organism that already had mitochondria or (b) ...


18

There is evidence that cells can exchange mitochondria. There are some donor cells that transfer mitochondria to recipient cells via cytoplasmic nanotubes (within the same species). This happens endogenously and triggering factors may include stress. References: Pasquier et al. 2013 Ahmad et al. 2014 Wang and Gerdes. 2015 Hayakawa et al. 2016 On ...


17

I think @mbq has covered the frequency question better than I can. There is at least one modern example of this kind of new organelle formation. Aphids have a deep, intracellular endosymbiont Buchnera involving some genome transfer that has developed in the last 200 million years. There are many articles about this topic (eg: Nature from 2000), and it ...


15

This is one of the most intriguing questions of eukaryotic evolution. As far as I know and have read, the autogenous theory is not accepted. There are quite some reviews on this topic. Also there is a wonderful book by Nick Lane on mitochondria called Power Sex and Suicide. You would be interested to read it. There are no sufficient evidences for the ...


14

Short answer: According to the definition of life, yes, Mitochondria are "dead". To be considered alive an organism must meet the following criteria: organized structure performing a specific function an ability to sustain existence, e.g. by nourishment an ability to respond to stimuli or to its environment capable of adapting an ability ...


13

In addition to S Pr's excellent example, I wanted to point out that some very recent research describes some special behavior in oocyte development specifically related to mitochondria selection. Here's a easy-to-read version: https://www.sciencedaily.com/releases/2019/05/190515131741.htm Here's the original version in Nature: https://www.nature.com/...


12

I would like to expand a bit on SolarLunix's post, because the logic used in the conclusion would also mean that endosymbionts, such as https://en.wikipedia.org/wiki/Buchnera_(bacterium), who cannot survive outside their host are also "dead". I think many of us disagree with that notion, so instead I would say that it's the fact that so many of their genes ...


11

Mitochondria are comprised of ~3000 proteins. However, the mitochondrial genome has only 13-14 protein-encoding genes. The remaining 99.6% of mitochondrial proteins are encoded by genes in the nuclear genome. (Wikipedia) Chloroplast genomes are only slightly larger (~100 genes). Gene regulation and signaling between the nucleus and mitochondria (and between ...


11

...would then be his offspring at risk? Why? No. Generally speaking, fathers do not pass on their mtDNA (Mitochondrial DNA). Why? Because the mitochondria present in oocytes (egg cell) is the mother's, as every oocyte directly inherits the mother's mitochondria when they are made in the reproductive organs. The mitochondria that the sperm from the father ...


11

The way we were To understand why you may encounter ATP synthase referred to as ATPase, you need to be aware of the historical context — the experimental work that preceded the knowledge of the structure and function of the enzyme complex that we have today. In a nutshell: Original studies of the components of what we now know to be a complex capable of ...


11

A typical animal cell has 1000-2000 mitochondria. From a statistical point of view, assuming a random distribution of the mitochondria and that the cell splits in half, the probability of having 0 mitochondria is (1/2)^1000 or 9e-302. This makes it an impossibility for all practical purposes. With enough mitochondria, a process to ensure the cell splits ...


9

There are metabolic processes in which ATP is synthesised without the involvement of ATP synthase. The best examples are, in fact, two steps in the glycolytic pathway, catalysed by phosphoglycerate kinase and pyruvate kinase. This is why, in the absence of any aerobic metabolism, many organisms (like yeast for example) can grow quite happily, producing two ...


9

If we were to suppose, as in the question, that all the mitochondria in a cell 'died' ('were irreparably damaged' would be better, as they are not independently alive) without any other consequences the cell would have no way of regenerating them. Even if the cell had another source of ATP (see @another 'Homo sapien' comment) such as anaerobic glycolysis, ...


9

This is slightly depending on which reaction you want to include into the cycle. I count four: One when Pyruvate is converted to Acetyl-CoA, one when Isocitrate is converted to α-Ketoglutarate, one for the reaction of α-Ketoglutarate to Succinyl-CoA and finally one for the reaction of Malate to Oxaloacetate. If you see the reaction of ...


7

I would say it has to do with the amount of mitochondrial or sequence that has been transferred to the host genome. As a consequence of all this information stored in the host genome, mitochondria cannot reproduce without the host. In this way, they are not their own organisms, but rather organelles. Over evolutionary time, the line between organelle and ...


7

In general, $\ce{NADH}$ and $\ce{FADH2}$ are coenzymes. The structure of the main part of an enzyme determines which coenzyme or which prosthetic group will work with the concerned enzyme. Unlike most other TCA cycle enzymes, Succinic Dehydrogenase involves the participation of $\ce{FAD}$ rather than $\ce{NAD}$ and that is a consequence of its specific ...


7

Maternal inheritance of mitochondrial DNA is very well conserved, although some species, such as some mussels, show paternal inheritance. As for why or what the advantage is, some of it is due to basic logistics: sperm cells have ~100-1000 mitochondria, egg cells have 105-106, so male contributions are largely washed out. Plus, most mitochondria in sperm ...


7

The short answer is, as you found, that mitochondria are wrapped in a double membrane and are thus harder to penetrate with antibiotics. The long answer is some of them do. Good antibiotics target structures widely found on and conserved in bacteria that are not found in human bodies. Some antibiotics are a little less specific and can indeed interact ...


7

What is difference between plastid, chloroplast and mitochondira? Plastid is a general term for an organelle which consists of Chloroplasts, Chromoplasts, Leukoplasts/Amyloplasts and Apicoplasts. Chloroplasts (Chloro = green) are involved in photosynthesis; they express Chlorophylls and have the thylakoid structures which are involved in the electron ...


7

I do not have a definitive answer but I can argue that mitochondria came into existence before chloroplasts despite the fact that, between their free living ancestors- $\alpha$-proteobacterium and Cyanobacteria, the latter seems to be older in evolution. I have following points to support this argument: The organisms that have chloroplasts also have ...


7

According to my knowledge, this was the molecular and cellular evolutionary path of life. Synthesis of essential building blocks (fatty acids, aminoacids, cofactors...) Condensation of building blocks First RNA replicase; RNA genomes (differentiation between genomic and functional RNA, primitive metabolism) Ribosomes and first matrix dependent ...


7

The answer is a bit more complicated than that. Mitochondria contain their own genome called mitochondrial DNA (mtDNA), encoding 13 proteins that are part of respiratory complexes I, III, IV, and V, 22 transfer RNAs (tRNAs), and two ribosomal RNAs (rRNAs). The separate tRNAs and rRNAs are necessary because the mitochondrial genome uses a slightly different ...


7

I think the question is based on a false premise: Poster: Now, mitochondria are said to have been archaea, right? Me: Wrong, I’m afraid. The closest bacterial relation of mitochondria is Rickettsia, an alpha-Proteobacterium (see Lang et al. for a review). Rickettsia is a eubacterium, not an archaebacterium. The confusion is probably due to ...


6

The passage of protons through the FO (membrane) portion of the molecule (driven by the electrochemical gradient of protons across the respiratory membrane) generates torque at the interface between the a and c subunits. This mean that the ring of 10 c subunits rotates relative to the a subunit. The γ subunit in the stalk rotates along with the ring of ...


6

The textbook version for the regulation of ATP involves a feedback loop with phosphofructokinase (PFK). The relative concentrations of ADP and ATP are characteristic of the energy state of the cell. If the cell is using energy, then there will be an excess of ADP. If not, then ATP. ATP is an inhibitor of PFK, which in turn slows glycolysis (thus reducing ...


6

It depends of what you call endosymbiosis. In the sense of mutualistic interaction between host cell and intracellular organism, it also include Rhizobium bacteria and Fabaceae plants, some Cnidaria and algea in their cells, and even some micorrhizal fungi that invade into plants cells. But parasitic interactions are also sometimes call symbiosis, as ...


Only top voted, non community-wiki answers of a minimum length are eligible