by denying it the necessary ingredients for the production of ATP, can it be restarted?
If you stop a cell
by denying it the necessary ingredients for the production of ATP, can it be restarted?
Depends on how you do it I think?
Technically yes. As a worst-case scenario, you could boil it down and make a new, functioning cell out of those pieces (plu the ingredients that were lacking).Originally Posted by tcaudilllg
Actually, Subterranean's answer was probably better.
LII-Ne
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Hmmm I'm not a pro on cells, but if I were investigating this question
I would first look at the conditions for cell life and death, as well as a clear understanding of the ATP cycle, and first see if any interruption in the ATP cycle will lead to a condition for cell death being satisfied, and secondarily if so (cell death occurs), if there are any variables that can be modified to reinstate the necessarily conditions for cell life.
My intuitive guess is that the cell probably has a certain amount of backup resources it can depend on if a problem occurs in its ATP cycle, but the cell will run less efficiently and eventually die if it doesn't return back to normal functionality. I'm also guessing that a cell once dead can't be restarted, as their would be little sense in cells reproducing and multiplying.
Also I tend to think there is probably a method to create cells in a laboratory or to re-vitalize them, but these methods are likely crude, and will always require a greater investment in energy than if the cell had not died. My guess for this is the 2nd law of thermodynamics, building a precise chemical structure of components would be at a lower entropy than a random soup of disoriented molecules. Since entropy must always increase by the currently observed laws of physics, even the most efficient process of constructing a cell would require at least the difference in entropy between a dead and alive cell.
This is just purely intuitive, I'm sure there are some work-arounds, and I'm fascinated to see what the new forefront of medical technology will be. In fact the creation of life and the 2nd law of thermodynamics always seemed to contradict itself.... how does a highly ordered and structured organism spontaneous appear when it would seem to be at a higher entropy than a mere soup of organic molecules...... is it only possible because our highly ordered existence depends on creating more chaos and entropy in the universe until life is completely non-existant? Apparently so, unless an exception to the laws of thermodynamics exists, which I'm kind of hoping it does.... thermodynamics and entropy is so depressing compared to something like astronomy were you talk about the creation of worlds and distant universes, thermodynamics talks about everything falling apart eventually into absolute cold and darkness.
All the 2nd law of thermodynamics says is that given enough time any organized system will break down. It doesn't say how much time, only that it will eventually happen. It does not forbid that a disordered system be reordered.
That I understand, when ATP stops, the motion of the cell stops as well. Assuming no bacteria or pathogens, the cell will remain inert. The cell does not really use ATP as an energy source... rather, it is the process of creating ATP which keeps the cell's parts in motion, therefore making the whole "alive".
I don't know why people have to overthink this. It is a very everyday occurrence that cells can be deactivated by supercooling, and then later be reactivated, for example.
link?
Actually you probably don't understand it as well as you think you do, I don't understand it as well as I could, and I've spent a considerable amount of effort towards understanding it.
The statement it does not forbid a disordered system be reordered.... yes it does, the law says "entropy must always increase".... reversible processes have 0 change in entropy. There is no such thing as negative change in entropy as a system moves forward, unless it draws its energy from a reserve which increases in entropy by at least the same amount. Generally what is intuitively referred to as order is rigorously defined as entropy which has a statistical definition and a thermodynamics definition using mathematics.
What I was taking about was this.... http://en.wikipedia.org/wiki/Heat_death_of_the_universe as applied to biological systems.
Last edited by male; 12-21-2010 at 01:48 AM.
lol that isn't cell death though.... freezing just slows the chemical reactions and metabolism. The cell is still functioning, just at negligibly slow rates and is therefore effectively "shut down". And freezing a cell requires a power source to power a refridgerator, which creates entropy =p.
I don't think tcaudilllg said anything about cell death, or about a means that didn't require power.
I don't know if it's possible to completely stop the chemical reactions in a cell by freezing without irreparably damaging the cell - I don't see why not.
Well that is true, if you slow the cell down by cryogenicly freezing it, you can stop ATP synthesis and then restart it. The downside is you stop everything else and slow it down and it requires significant resources and technical skill.
I think originally I was more thinking along the lines of a cell is starved of ATP, like that resource is neglected from the cell. Freezing it would be more like slowing the process down rather than starving the process of its resources.
Well, it depends on what kind of cell we're talking about. Certain types of cells in the domain Archaea, for example, are adapted to forming "shells" of sorts when nutrients are scarce, only to leave the shell once nutrients reappear. Prokaryotic cells, in general, are designed to survive because a dead organism can't pass on its genes. It would be greatly advantageous for a prokaryotic cell to be able to survive in harsh conditions.
The same couldn't exactly be said for a Eukaryotic cell. Save the group of single-celled Eukaryotes archaically referred to as "Protists," Eukaryotic cells are designed to die. This is such a central part of multicellularity that the refusal of cells to die causes a horrible disease. (that is, cancer) It's much easier to create a new cell than to save a dying one. This is a distinct advantage of multicellular Eukaryotes as they can lose a cell without losing the genome of the organism.
And that, in short, in the answer to your question from a Biological standpoint: a dead cell is a dead cell.
In reality, however, it would depend on how long the cell had been inactive. A cell will decompose without a constant energy source to prevent the intermolecular forces within the cell from ripping it apart. The less time a cell spends decomposing, the greater the chance it would able to resume functioning. You'd need an empirical test to see how long this period is.
ah.
I've heard that you can stop mitochondria committing mass suicide as a result of some mortal injury aquired by the large body via freezing - i.e. it merely prolongs their life - but clearly, if it prevents mitochondria dying, then the process could be reversed, with ATP again being produced. The critical thing to me is whether such a process can be used indefinitely.
what causes mitochondria mass suicide in cells that sustain injury?
The "death" of the organism that the mitochondria is in symbiosis with.
(I meant to say "larger body" before.)
Interesting read, by any chance do you know the stages of cell death?
I'm not sure as to what happens to a cell without energy and how it decomposes. I can, however, make some notes about programmed cell death, apoptosis. For instance, it's worth noting that the mitochondrion, the main site of ATP production, stay intact for the duration of the cell's death and provide energy for the process, which is essentially the breaking of cellular components into their "building blocks" and packaging them in neat little membrane sacs, which are then absorbed, usually by the organism's immune system. The significance, as it pertains to this thread, is that death is, normally, an energy-mediated process.
Supercooling inhibits atomic diffusion, thus preserving the order of the cell. But if an active cell is denied essential nutrients, it cannot maintain itself in the required manner and there is nothing stopping the eventual slide into disorder and cell death.
So my thinking goes, anyway.
SLI/ISTp -- Te subtype
That's fascinating... if you stopped the ATP synthesis, could you stop the cell from dying?
Yes, you would stop it from killing itself... by depriving it of energy.
It's analogous to preventing suicide with murder.
It seems like it would be like shutting down the power source of the cell, while it wouldn't carry out its own deconstruction, it would exist as a disfunctional cell... which is potentially a hazard having disfunctional cells build up and take up space.
Another important question is why do cells die? This is a good question, because everyone immediately assumes cell death is negative, like its been mentioned cell death is important to prevent cancer and such. Cell death may serve a utilitarian purpose.
Fascinating. I don't get half of what you guys are talking about, but the concept is truly fascinating.
Okay, leaving the nerdfest now...
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Thats correct.... cooling affects matter in two ways....
it affects the population distribution of various energy states of atoms and molecules
and it affects the presence of vibrational modes in the atomic lattice of solids
When things cool there is a smaller probability of a higher energy state being populated by an atom. When cooled to very very low temperatures most atoms and molecules are in their ground state. In fact bose-einstein condensates depend on forcing everything to their ground state. When they are in this ground state they exhibit amazingly odd properties like superfluidity. But that isn't important... what is, is that atoms in lower energy states have less probability of breaking across barrier potentials and therefore remained confined.
Second higher energy vibrational modes require more energy. So when something cools higher modes become less excited and only the lowest modes of vibration remain in a lattice structure and atoms become more localized and oscillate less.
See http://en.wikipedia.org/wiki/Equipartition_theorem for an intro to lattice structures and molecular vibrations
See http://en.wikipedia.org/wiki/Boltzmann_factor to learn about probabilities that atoms are in particular energy states
As I understand it, a magnetic reaction causes cell intake across certain gateways in the permeable membrane/lipid bilayer. So that's how chemicals get inside the cell... but how does the cell use them?
When an organ dies from lack of oxygen, it's hardly utilitarian.Another important question is why do cells die? This is a good question, because everyone immediately assumes cell death is negative, like its been mentioned cell death is important to prevent cancer and such. Cell death may serve a utilitarian purpose.
One thing I've been thinking about is the feasibility of restoring life to bodies frozen in cryogenic chambers.
Fascinating. I don't get half of what you guys are talking about, but the concept is truly fascinating.
Okay, leaving the nerdfest now...
lipids are polar molecules that are electrically charged in areas (polar molecules). It uses electromagnetic repulsion like that in magnets to repel certain molecules out and allow certain molecules in. There are several ways things get into cells. The study of such is called Cell Transport. There is more than one way, for example their are ion channels, proton pumps, diffusion, and so forth. There are even molecules which act as "ferries" transporting molecules in the cell. An example of the ferry concept is how hemoglobin is transported via blood cells. In sickle cell anemia the structure of the cell changes and there isn't sufficient hemoglobin to transport hemoglobin and anemia develops.
Anyways I think the cell uses different chemicals differently. Best way to find this out is looking into cell transport, especially where they discuss examples. If any specific details are required, then try to look up cell transport for particular types of cells in the body that have been studied by biologists.
Check out http://en.wikipedia.org/wiki/Proton_pump for example. In cell respiration it will take in H+, or protons via proton pumps and once inside the cell these ions act as a method of charging the cell to a higher potential which organelles draw from to carry out respiration (think of the higher potential like an electrical capacitor or a water tower). The protons H+ I believe are a major component required in ATP synthesis.
That's very interesting, Lucid. Seems like you're something of a sponge for that stuff.
Physics is my degree I just got, so I've taken some natural sciences classes, but I prefer the physics/math/engineering stuff over biology. While biology is very fascinating, there is a lot of memorization of processes. I remember about transport theorem though because it had a lot of thermodynamics involved and that was the semester before I took thermodynamics, which was a good semester... it was the semester I got off academic probation after a long time on it from a single bad semester I had 2 years before, it was the semester I got great grades, and it was the semester I got to expand my social ties and get to know a lot of interesting people, everything up to that point was a struggle. Now a new set of problems was dealt =(, I would totally relive that semester though, it was glorious =).
So memorization of processes is something you're not particularly good at?
I don't know, that's far too general. The only thing I know for certain is I found all the memorization of chemical processes deathly boring and tedious when I took the class.
I like processes in general though, especially understanding the mechanics and cycles of things.
Though in the class everything was presented far too detailed and step by step, and it just didn't read very streamlined. A lot of facts and details were elaborated on at each little step and it kind of destroyed any ability for the reader to grasp an overarching concept.
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