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16

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

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.


14

Well, it seems quite obvious that it was not a single I-eat-you-but-you-survived act but rather a convergence of endosymbiotic and host species into a greater and greater cooperation. Of course this leaves a question if there was one or more species of endosymbionts involved. Mitochondria are a very primeval story forced by the oxygen catastrophe, so it is ...


11

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) ...


8

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 ...


8

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 ...


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

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 ...


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 ...


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 ...


6

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 ...


5

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 ...


5

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 ...


5

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 ...


4

For starters, see this thread. My understanding is that the ancient predecessors of mitochondria were free-living unicellular organisms. Supposedly at one point, these mitochondria-like cells developed an endosymbiotic relationship with a larger cell. This relationship was advantageous for both cells: the smaller cell could focus on energy production, ...


4

It's hard to understand the question, but in any immunocytochemical staining such as the above, you have two different types of reactions: the antibody binding to the target (in this case, some laminin) the peroxidase-based colorimetric reaction with DAB. DAB (3,3'-diaminobenzidine tetrahydrochloride) is oxidized in the presence of hydrogen peroxide to ...


4

In general, $NADH$ and $FADH_2$ 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 $FAD$ rather than $NAD$ and that is a consequence of its specific structure. Another ...


4

We know about nuclear DNA having a mitochondrial origin mainly in two ways: (1) a sequence in the nucleus is found to closely match a sequence found in mitochondria, or (2) mitochondrial proteins are found to be encoded by the nuclear genome but not by the mitochondrial genome, and those proteins seem likely to have been necessary for sustaining life of the ...


4

Interesting question. I researched this a bit now and the phenomenon is termed "numt" for "nuclear mitochondrial DNA". This term descrives the transfer of cytoplasmic mitochondrial DNA sequences into the separate nuclear genome of a eukaryotic organism. It seems that most of these sequences are inactive. This list at pseudogene.net has a large number of ...


3

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 ...


3

Mitochondrial DNA is circular, like bacterial DNA, and around 16.6 Kb long. It codes for 37 genes in total but the majority of these are simply the machinery for gene expression (curiously, mitochondria have a slightly different codon->amino acid translation 'table' to nuclear DNA) and so just 13 code for proteins. Single mitochondria usually have multiple ...


3

This step is catalyzed by succinyl-CoA synthase which has two different isoforms- one which produces GTP while the other produced ATP. It seems from this study that predominantly anabolic tissues prefer the GTP-producing form whereas the predominantly catabolic tissues use the ATP-producing from. In the same paper they discuss that GTP is important for ...


3

This is well-explained at the Wikipedia page on skeletal striated muscle. There are two principal ways to categorize muscle fibers: the type of myosin (fast or slow) present, and the degree of oxidative phosphorylation that the fiber undergoes. Skeletal muscle can thus be broken down into two broad categories: Type I and Type II. Type I fibers ...


3

This link seems to have good information that answers most of your questions. In my mind, there are two types of mitochondria: ones that work and ones that don't. Mitochondria do have DNA but that mDNA is there to encode proteins for their specific functions (e.g. to create ATP). So, although the mDNA may not be uniform for every mitochondrion in your body, ...


3

The concept you refer is recognized as mitochondrial biogenesis and it is regulated by AMPK which senses the cellular energy demand. If you have few mitochondria in the cell, the electron transport chain works suboptminally generating less ATP. When the AMP/ATP ratio is high (low ATP) AMPK is activated, and turns on the catabolic pathways required to produce ...


3

EDITS - I appreciate the comments and have incorporated them here. Thanks to @Superbest and @user22406 for raising them. I hope this makes a better answer for the community. Under normal circumstances, genomic (self) or mtDNA released into your cell or body cause absolutely no (known) problems. I'll explain why that is, how the body can detect ...


3

Yes. But it is incorrect to call mitochondria an organism now. Most of their genes were lost and are now encoded in the nuclear genome It gets most of its metabolites It is not known. See the other post for details. Why membrane: I guess you know that. Why folded: you guessed right. Only ovum donates mitochondria and other cytoplasmic factors. Sperm just ...


2

There are evidences of secondary endosymbiosis i.e. organelle within an organelle. This is quite evident in Chromaveolates. Many unicellular Chromaveolates which had been classically referred to as unicellular Algae, have chloroplasts derived from other algae. This organelle in turn has a membrane bound suborganelle. For a quick reference you may see this ...


2

well.. from the evolutionary point of view the eukaryotes acquired these metabolisms (except glycolysis) from their prokaryotic endosymbionts. Not all prokaryotes have the ETC. The free living ancestor of mitohondria is supposed to be the alpha-proteobacterium. Now, glycolysis is a common pathway in lot of lifeforms perhaps because of abundance of glucose. ...



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