38
votes
Are mitochondria dead?
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 ...
- 15.2k
25
votes
Accepted
Are cells guaranteed to get at least one mitochondrion when they divide?
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 ...
- 6,182
18
votes
Accepted
Are mitochondria transferable between cell types, individuals and species?
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 ...
- 35.2k
14
votes
Are mitochondria dead?
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 ...
- 3,074
13
votes
Are cells guaranteed to get at least one mitochondrion when they divide?
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.
...
- 407
12
votes
Are mitochondria dead?
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 ...
- 360
11
votes
Are cells guaranteed to get at least one mitochondrion when they divide?
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 ...
- 241
10
votes
Why is ATP synthase sometimes referred to as ATPase?
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 ...
- 24.1k
9
votes
Accepted
Can mitochondria be regenerated by the cell?
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 ...
- 24.1k
9
votes
How many molecules NADH are produced in the Krebs Cycle?
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-...
- 51.3k
7
votes
Do mitochondria contain the genes to specify themselves?
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, ...
- 15.2k
7
votes
Accepted
Why do mitochondria have a phospholipid bilayer?
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 ...
- 24.1k
7
votes
Accepted
How is a very small quantity of poison able to kill a large organism?
"Cyanide" doesn't refer to just one compound, but given the lethal dose you mention of "half a gram" you are probably referring to potassium cyanide, with a molecular weight of about 65g/mol, so 0.5 ...
- 42.9k
7
votes
How can the leakage of mitochondrial protons generate heat?
Uncoupling ATP synthesis from the ETC (electron transfer chain; this is where oxidation takes place) by thermogenin or any other method means that the energy used to generate or uphold the proton ...
- 4,391
7
votes
If there is such known "Mitochondrial Eve", does it means that all the mitochondrial dna in everyone's body is same?
The mitochondrial genome has a nonzero mutation rate, though estimates differ according to method. Estimates are approximately $10^{-8}$ per bp per year on average, and the mt genome is $\approx20,000$...
- 8,862
7
votes
Accepted
What keeps mitochondria from multiplying out of control?
I'm guessing at the motivation for your question -- In the evolutionary history of eukaryotic cells, mitochondria were once free-living bacteria. What prevents them from acting as intracellular ...
- 8,246
6
votes
Accepted
Why don't protons diffuse out of the mitochondria during chemiosmosis?
Diffusion, is by definition (Ficks Law) describing movement along or against some gradient (here its concentration) even if the mechanism of transport differ: active, passive, facilitated. The setup ...
- 397
6
votes
Accepted
Can mitochondria become cancerous?
Interesting question.
As a prelude, I should probably mention that single celled organisms cannot get cancer as we understand and define it. Mitochondria are not, of course, single celled organisms, ...
- 8,751
6
votes
If there is such known "Mitochondrial Eve", does it means that all the mitochondrial dna in everyone's body is same?
The M.DNA mutates about 1% in a million years, and because our Mt-Eve is 150,000 years old, our mitochondria are 0.15% different, or 99.85% the same globally, and 99.95% the same in Eurasia.
The ...
- 10.3k
6
votes
Accepted
How does mitochondrial uncoupling enhance performance in muscle cells?
Skeletal muscles have multiple systems that increase the rate of energy generation in response to faster energy consumption during excercise.
System
Rate
Sustainability
Phosphagen
highest
10-15s
...
- 224
5
votes
Accepted
Origin of the double membrane of mitochondria and chloroplasts
The answer lies in the protein composition of mitochondrial membranes, which undoubtedly prove that the outer membrane (OM) is of alphaproteobacterial origin, and the phagosomal membrane (if there was ...
- 241
5
votes
Accepted
How did mitochondria make energy long ago?
You are asking a very interesting question.
As you correctly mention, the substrates of mitochondrial metabolism (TCA or Krebs Cycle) are pyruvate and NADH, and, through oxidative reactions, ATP is ...
- 134
5
votes
Accepted
How many protons are pumped out per pair of electrons from NADH in oxidative phosphorylation?
It seems like the mistake is in complex III. Look at this image from here:
It clearly shows the number of protons reduced in (and taken from) matrix and number of protons pumped into inter-membrane ...
- 14.1k
5
votes
Are mitochondria dead?
What a brilliant question for promoting a discussion. Mitochondria definitely reproduce, they maintain a better energy flow than any other part of the cell, and they maintain a very low entropy state ...
- 51
5
votes
Why is FAD, rather than NAD+, reduced in the succinate dehydrogenase reaction of the Tricarboxylic Acid Cycle?
There is a simple straightforward answer to this question, which I present here because the poster of the accepted answer seems unsure which of his three suggestions is correct, and therefore there is ...
- 24.1k
5
votes
What will happen if mitochondria had a structure like lysosomes?
Mitochondria are double membraned organelles with an outer membrane which is a rod-like shape, and a convoluted inner membrane (Figure 1).
Figure 1
On the other hand, a lysosome is a single-...
- 636
5
votes
Accepted
Protein-coding introns in mitochondrial genomes
Mitochondrial genomes differ greatly in size, coding potential and even whether they are circular or linear. Mammalian mitochondrial DNA is small (11–28 kbp) and intronless. However the mitochondria ...
- 24.1k
5
votes
Accepted
Is Chemiosmosis a hypothesis or a theory?
Preamble
Although there is a case for closing this question (it is two questions, the first of which is more linguistics, logic or philosophy of science, and the second well-covered in text books) I ...
- 24.1k
4
votes
Are mitochondria transferable between cell types, individuals and species?
I'm not entirely sure about cross species organelle transfer (lets focus on mitochondria), but some people have already made three parent babies, therefore mitochondria are at least transferable ...
- 133
4
votes
Accepted
Genetic Diversity in Mitochondria
Your claim that "there is a lack of genetic diversity" in mitochondria is not correct. There is no connection between recombination and mutation rates per se. In fact, mitochondria have much higher ...
- 2,929
Only top scored, non community-wiki answers of a minimum length are eligible