Cell-Division is a 'clone-copying' process ???

[Widdekind]

Please ponder the process of simple Cell Division, in simple single-celled organisms. Presumably, the single cell starts with some mass (m), "eats" biologically important molecules, "fattening up" on those "parts", until it masses about twice its original mass (m --> 2m). Then, it uses those "parts" to duplicate all of its cellular systems, and divides, into two daughter cells, each of approximately the original mass (2m --> m+m).

 

QUESTION: Imagine being able to track all of the individual atoms, inside the single cell. Imagine being able to 'tag' those atoms, labeling them as "original" or as part of the "parts" supply. Then, when the cell uses the "parts" to duplicate all of its cellular systems, do the "original" and "parts" atoms get mixed and mingled; or, after Cell Division, do all of the "original" atoms remain together, in one of the daughter cells, whereas all of the "parts" atoms were assembled, into the the other daughter cell ???

 

In some sense, in the "bio-molecular dance of Life", the original single cell is a little like a dance floor, full of active bio-molecule "dancers". Then, the cell "eats", consuming "parts", which are a little like new bio-molecule "dance students", who enter the dance floor, and (somehow) become "partnered" with the original "dancers" already on the "dance floor". The "original dancers" then "instruct the new students in the waltz dance". And then all the "partnered pairs" separate, in two distinct "dance squads", at opposite ends of the "dance floor". When that happens, does the "original dance squad" remain together ??? Does the "original roster" remain the same ??? Or, do the active bio-molecule "dancers" swirl around the "dance floor", and all the "trainers" & "trainees" stay stuck together, 'on the same team' ???

 

(thanks very much in advance, for any kind of clarification, of any of the considered concepts)

[Mr Skeptic]

There will be some mixing. The cytoplasm, for example, is not magically kept separate just because it is for a copy. The various proteins are copies off of genomic info not off of other proteins. As for the DNA strands, for those there is an original and a copy, but I don't think that all the originals and all the copies get separated in the same direction. Maybe, but I don't know.

[pioneer]

If you look at just the DNA, each strand of the double helix becomes paired with a newly fabricated partner. At least for the DNA, the DNA of each next generation daughter cell is half old and half new. If those two cells then duplicates their DNA for cell division, one strand of the grandparent DNA remain as well as one strand of parent DNA, each paired with even newer strands. The cells may also work to better pair the strands adding a little new to old or new to new.

Edited December 3, 2010 by pioneer

[CharonY]

Widdekind, the error in that picture is possibly based on the assumption that there is some kind of base state that consists of defined elements. A cell, however, is in constant flux. There is, for instance generally, not necessarily a standard mass m, but rather it would be the minimum mass, immediately after the division. Depending on situation the cell could stay at that for a while, increase mass up until a certain extent without division, or increase mass with division. Cell division regulation is not necessarily coupled to cell mass. In addition, none of the daughter cells is really the original cell. Both really are. The original cell just formed a septum and split itself in two. Except in cases of budding both are pretty much equivalent and it is pretty much arbitrary to define one of the cells as the original.

 

In bacteria you could anchor it on the original DNA molecule, as during replication a second one is formed and moved to the other side of the cell division site. For eukaryotes this is not possible as during mitosis each half of a chromosome gets moved to each new cell. It is purely by chance whether it is the newly synthesized chromatid or the original one.

 

Pioneer, you are heavily confusing meiosis with DNA replication. That is not helping.

[pioneer]

Technically it is not mass but energy value that is stored, since not all chemical mass has the same energy value (compare CO2 to the lighter CH4). The cell needs to turn the mass/energy of food chemical states into energy to drive all the processes needed for the cell to divide. Fats are worth more pound for pound that say proteins. Protein synthesis represents an energy downgrade from the original energy stockpile. If it was not we would be creating energy out of the void which is in violation of energy conservation.

 

The cell climbs an energy hill and then falls down the other side to make two cells. This is similar to the activation energy of any chemical reaction, with the cell needing to climb its own energy curve until it begins to slide down the other side using a very repeatable conversion process. The new lower energy state of two daughter cells then climb their own energy curves.

 

There are exceptions where some cells, like ovum, store enough energy for many conversion cycles; step down the initial stored energy using many stages. Once this stored energy is used up the process stops dividing but may continue to it lowest energy configuration or steady state shape. For the cells to climb more energy hills, the blob will need to attach to the uterine wall so energy can be inputted. If we look at the sum of the parts, after attachment, the entire integrated growth is gaining mass/energy. The bulk curve is going up a huge energy curve, while the single cells are going up and over, with each differentiation impacting the up and over curves so the bulk curve can go up.

 

As far as material division, say we look at the nuclear membrane, late in cell cycle; it disperses. To overcome the attractive forces that had held the nuclear membrane together, we need to increase the energy of the nuclear membrane for it to gain entropy for dispersal. The descent down the bulk energy curve of the mother cell, is directly and indirectly supplying energy which helps the nuclear membrane material climb its own energy curve. The fact that this material divides and doesn't just reform in whole, implies it doesn't just back down the energy push, but goes up and over to a new final divided state. In the process of being of high entropy/energy the original distinction of position and place is less important. There is mixing of new and old.

Edited December 3, 2010 by pioneer

[Widdekind]

Thanks very much for all the responses.

 

 

 

Widdekind, the error in that picture is possibly based on the assumption that there is some kind of base state that consists of defined elements. A cell, however, is in constant flux. There is, for instance generally, not necessarily a standard mass m, but rather it would be the minimum mass, immediately after the division. Depending on situation the cell could stay at that for a while, increase mass up until a certain extent without division, or increase mass with division. Cell division regulation is not necessarily coupled to cell mass. In addition, none of the daughter cells is really the original cell. Both really are. The original cell just formed a septum and split itself in two. Except in cases of budding both are pretty much equivalent and it is pretty much arbitrary to define one of the cells as the original.

 

In bacteria you could anchor it on the original DNA molecule, as during replication a second one is formed and moved to the other side of the cell division site. For eukaryotes this is not possible as during mitosis each half of a chromosome gets moved to each new cell. It is purely by chance whether it is the newly synthesized chromatid or the original one.

Please ponder the following scenario:

 

1. Take some simple cell
   
2. Put it into "torpor / sleep"
   
3. Invasively, but non-lethally, "rip out all of its protein molecules" (say)
   
4. Invasively, but non-lethally, "replace all the removed protein molecules" with artificially synthesized duplicates
   
5. Wake up the cell
   

Q: Does the cell care (about being given a complete "blood transfusion exchange" [in rough analogy]) ?

[Mr Skeptic]

The cell won't "care", except for the fact that you can't actually do that. Current technology is nowhere near being able to do it.

[pioneer]

The daughter cells are less concerned with particular atoms and molecules as it is with the molecular configurations it ends up with. Cells can continue to function without the DNA, such as red blood cells. However, they will not be able to replicate. For red blood cells this is practical thinking, since you don't want the red blood cells clogging the blood supply sliding up and down their energy hills to the beat of their own drum. It is better to use a feedback loop and input new red blood cells from a regulated source.

 

The reverse is not the case. We can not remove the rest of the cell and leave only the DNA and expect the cell to return to normal. The DNA needs the logistics of a minimum functionality within the rest of the cell, with being closer to the mother cell, conducive to not only reestablishing all the needed functionality, but the differentiation of the DNA. For most cells, they have more DNA than they need. To help distinguish what the mother cell used from what remains packed away, feedback is needed from the cytoplasm.

 

This is more obvious in multicellular differentiation, where the chromosomes are the same for all cells during cell cycles, and the DNA is taken off line. The cytoplasm of the daughter cells will have the configurational capacitance to feedback the DNA differentiation. In the case of a growing embryo, where cells need to be differentiating, the original mother cells are not the goal. Rather the goal is new cell types. In this case, the cytoplasmic capacitance needs to shift. If we start with a stem cell, and place it near other cells, we will get external feedback through the cytoplasm to differentiate the DNA. What is happening is the feedback is altering the energy curve in terms of the energy hill and the position of the final valley, with the DNA differentiation defined by that final valley.

 

The reason the global energy hill is important is it defines the state of the cellular water, which is the global wild card variable in contact with everything. If you need a certain trigger, the potential in the water will impact all the surfaces and surface activity. If we add things that can buffer the water, we could store more food energy, before the surface potential for the trigger is reached. The potential of the water will also impact the DNA configuration with packing having lower energy than unpacking. As the global water energy increases, due to cytoplasm activity of a daughter cell the equilibrium shifts to unpacking. This is also pushing the cytoplasm material in both shape and position to define equilibrium. The capacitance within the cytoplasm sort of sets the water potential to rough in the DNA configuration. The water is not sensitive enough to distinguish new from old molecules since its impact is for the global needs of the cell, to keep all the effects integrated.

Edited December 4, 2010 by pioneer

[Widdekind]

Thank you very much for the informative reply !

[Widdekind]

... Cells can continue to function without the DNA, such as red blood cells. However, they will not be able to replicate. For red blood cells this is practical thinking, since you don't want the red blood cells clogging the blood supply sliding up and down their energy hills to the beat of their own drum. It is better to use a feedback loop and input new red blood cells from a regulated source.

 

The reverse is not the case. We can not remove the rest of the cell and leave only the DNA and expect the cell to return to normal. The DNA needs the logistics of a minimum functionality within the rest of the cell, with being closer to the mother cell, conducive to not only reestablishing all the needed functionality, but the differentiation of the DNA. For most cells, they have more DNA than they need. To help distinguish what the mother cell used from what remains packed away, feedback is needed from the cytoplasm.

 

Thanks again !

 

This seemingly suggests, that the "magic" of Life, lies more in the "Metabolism", than in "Replication". To wit, such seemingly suggests, perhaps, a poignant parallel, to "macro-animal" instincts, wherein Survival (perpetuating Metabolism) = Instinct #1...

 

and Replication (sex) = Instinct #2.