Apoptosis, programmed cell death, serves as a regulatory role in multicellular organisms for the purpose of maintaining cellular integrity, determining embryological outcomes, and for getting rid of aged cells..

Apoptosis acts a mechanism to get rid of cellular waste with minimal damage to the underlying tissue; this is opposed to necrosis. This is accomplished by an internal caspase cascade mediated by either activation of the Fas receptor or TNF-R1.

Cells that undergo apoptosis have generally been damaged or altered past the point of reasonable repair or are "old" and past the point of use for the organisms.

Additionally, apoptosis plays a central role during embryological development; necessary for the formation of appendages and other bodily structures; your fingers form from web like structures due to programmed cell death of certain cells.

Roughly 50 billion cells undergo apoptosis each day in humans.

On a metaphysical level,cells must die to maintain the genetic integrity organisms. .

Apoptosis, programmed cell death, serves as a regulatory role in multicellular organisms for the purpose of maintaining cellular integrity, determining embryological outcomes, and for getting rid of aged cells..

Apoptosis acts a mechanism to get rid of cellular waste with minimal damage to the underlying tissue; this is opposed to necrosis. This is accomplished by an internal caspase cascade mediated by either activation of the Fas receptor or TNF-R1.

Cells that undergo apoptosis have generally been damaged or altered past the point of reasonable repair or are "old" and past the point of use for the organisms.

Additionally, apoptosis plays a central role during embryological development; necessary for the formation of appendages and other bodily structures; your fingers form from web like structures due to programmed cell death of certain cells.

Roughly 50 billion cells undergo apoptosis each day in humans.

On a metaphysical level,cells must die to maintain the genetic integrity organisms. .

I agree with Micheal.Ererything renews in the world.Spring comes and winter goes.There is a mechanism in the nature that omits malformations that may happen during life a cell and when the repair is not enough ,the cell dies.Also by this way i think the cells can coordinate with their environment.Life need esprit and vitality.

Search for apoptosis here http://www.nature.com/scitable and you will find some interesting articles.

Cells undergo apoptosis under physiological and pathological conditions. Different factors trigger apoptotic cell death.

Apoptosis is good thing :) if apoptosis isn't, maybe there is cancer. Because when cell cycles is going on, if cell has DNA damage, checkpoints stop it and cells undergo apoptosis. Not only DNA damage of course can be different factors too. And during embriogenesis, apoptosis is necessary, too.

Also, if a cell is infected with a virus, viral peptides will be presented on mhc I and a cd8 T cell will kill the infected cell by inducing apoptosis. This spares the rest of the body from death by the virus.

Also, once the virus is cleared, the cd8 T cells is no longer needed. So some will become memory for rapid response to a repeat infection but the majority of the cells will die. Otherwise, if you had the flu for example, your responding T cells would live forever and give you cytokine induced fever for the rest of your life and would likely have toxic effects to normal tissue.

Interestingly though, when it comes to cell turnover (replacing aged cells as above), there are likely specific reasons why some cells are regenerated (ex. intestinal lining) while other cells not regenerated in adults (neurons).

Perhaps I'm missing the point here, but for me the problem is why do cells 'need' to die? What is it that makes a cell become unable to continue to exist as it did at the beginning? Presumably at first it ingests and excretes without a problem. But then? .. What is it within the cell that fails to maintain the initial integrity? I believe some cells are effectively immortal; so why are not all cells so? Why do some cells 'age' more slowly than others? This seems to be a problem for higher organisms, but which such explanations as size don't fit - some small things live long, some don't.

i think it may relative with mutation. For evolution, mutation must be, but not all of mutation, Only good ones. And there is a lot of factors caused mutation (UV, Hipoxia, free radicals...etc). Several mutations have to be eliminated. This may done with the apoptosis. Maybe

All though counter initiative, Apoptosis typically has beneficial impact; "must be cruel, to be kind."

Cells are eliminated by apoptosis when they are produced in excess and only functional ones will remain. Some cells are needed transiently and also some cells die either because they are harmful or because it takes less energy to kill them than to maintain them. Cells are eliminated when not needed, or lose their function or when they are potentially dangerous to the rest of the organism. During embryogenesis the cells die because of remodeling and structuring of the body organs. All these processes are controlled by signals and very complicated pathways.

It is estimated that between 50 and 70 billion cells die each day due to apoptosis in the average human adult. For an average child between the ages of 8 and 14, approximately 20 billion to 30 billion cells die a day.

Thanks a lot professor,

Abdalla El-Mowafy im following your updates which helped me to learn new things.

Cells can be eliminated not only by apoptosis but also by autophagic and necrotic cell death.

I think for this you need to understand ageing process and study about telomeric sequences....

Non-functional or misfunctional cells must be eliminated from tissues for reasons of energy and space economy, however, many things influence this, for example, Telomere lenght and the enzymes that participate in Telomere reparation and growth, and at least one type of cells is 'eternal': the germinal cells that when replicate produce gametes, that after generation of a zygote willl give raise to a new being don't die, if the individual is not killed by an external agent and no reproduction of it took place.

The germ cell splits, one of the resulting cells may remain a germ cell, and the line never ends.

Some cancer cells have reached an 'inmortal' condition, it no longer have a limit of divisions as normal cells have, and can be grown in culture indefinitely, several molecular biology mechanisms may explain this.

At present im working on telomeres in cellular aging.Otherthan telomeres are there any other factors influencing it.

After a while its inevitable that the cell is going to start getting 'old', there's been a suggestion that perhaps the bonds holding proteins together in the cell are not able to be maintained and must be 'refreshed' (which is a little too sub particle physics/chemistry for my knowlege), but a a great example of why apoptosis and mitosis in tandem can be useful is endothelial cells, where membrane proteins are in constant interaction with outside influences that eventually damages delicate structures such as signalling proteins or membrane receptors. Its easier to make a batch of new ones and get rid of the old ones, rather than constantly trying to repair tiny parts of proteins. Thats the slightly more molecular answer to why, but how is something entirely different.

Apoptosis generally responds to signals from transcription factors such as p53, so for example if damage is found in DNA upon replication, p53 is recruited to up-regulate 'death factors' either intrinsically or extrinsically, which can lead to protease recruitment (caspase) which 'dismantle' cellular components.

As you have probably gathered from your research, telomeres get shorter each time a cell goes through mitosis so inevitably will become shorter which can aid senescence progress (unless you're a cancer cell).

A summary of the answer to what it seems your asking is that there is more machinery and mechanisms for apoptosis and mitosis than there are repair mechanisms for every time something breaks in a cell. It seems like its more energy efficient for an organism to simply make more cells than to repair them.

I hope this helps, its as accurate as I can make it!

Cells from multicellular organisms exist only in the context of other cells in time and space. A single cell, even if it is a stem cell, cannot survive on its one. I suspect that there probably are yet to be identified gradient of signals that must be necessary to maintain a threshold for cell survival. At present, empirical evidence is lacking to satisfactorily answer this very good question of single cell survivability.

To Harikrishna (or should I say to Reddy?) M A Blasco, head of the CNIO (Spanish Center for Oncological Research) www.cnio.es has a long time expertise in Telomere research, perhaps you can have some info from this basis. Salut

to replace the worn down tires in the case of the rbc's form being a disc like shape as i known it. it's nature recycling and improving the next time around.

How a bout neurons don't some survive for life? if not how is memory "stored" for life or maybee not as this neuron loss equals us forgetting ywt this was studied and research i belive revealed the neurons to survive yet be 'inactive" either way great question thank you for asking!!

Congratulations for your question about why a single cell can not survive, it is really an interesting question. To answer it You need to be more specific: Are you refering to a cell culture originated from a single cell extracted of some specific tissue? Or are you refering to an imortalized cell line In culture?

In some specific cases, for example to prepare a monoclonal antíbody, a single cell can and should survive and proliferate very well to produce monoclonal antibodyes.

Lifespan of RBC is 120 days in human and about 30 days in mouse. Life span is determined genetically. Programmed cell death is a conservative evolutionary process.

I'm referring to immortalised cell lines....n how do mutations occurs in cell lines.

Thanks a lot professor for your reply Patricia Clissa.

Sarah's response: "After a while its inevitable that the cell is going to start getting 'old'" really begs the question. My interest is precisely why and how such cellular changes happen. Given that how long this takes varies tremendously for different cells even in humans; plus there's been a story in the news recently of some sea organism that is thought to have a life-span of over 1,000 years.

Given that all life that we know of is based on the same DNA structure, and some of that is effectively immortal (that is, parts of our DNA is from the original DNA billions of years ago), then why cannot the whole cell be immortal?

Teleological thinking has been felt to be philosophically dubious for some time (that is, things striving to an end purpose, such as a 'need' to die), so any reasoning based on this is unsatisfactory.

And anyway, whilst there may be some 'advantage' to supposed selfish genes 'needing' to make cells die, I'd like to chose not to thank you. In one sense, any living things is constantly striving to stay alive as a whole, so how come there's this underlying 'need' to die off? Or maybe ageing is an accidental by-product of some faulty genetic coding that is rectifiable? After all, there's at least a handful of organisms that actually don't age in the normal sense - they get stronger/more fertile/etc as the age.

To successfully grow an immortalized hybridoma clone, IL-6 or briclone medium is used. Even here, the single cell has to be initially kept in a 96 well plate so that the dividing cells are kept in close proximity to keep the cells "talking" to each other. Thus, cells need to "know" where they are in time and space. Similarly, if one observes a fertilized totipotent zygote, as the blastomeres are produced, they are also kept crowded next to each other by the presence of zona pellucida, which creates a threshold concentration of multiple growth factors necessary for the embryonic growth. Another example is regenerating organisms mentioned by Ian. While the neoblast is essential to regenerate a chopped up planarian into whole organism, an isolated single neoblast cannot be maintained in culture for a prolonged period of time. Thus, while immortal organisms like hydra or planarian can successfully regenerate, individual cells from these organisms also die in culture. While the FoxO gene has been suggested to be necessary for the maintenance of stem cell-like properties from hydra to human, this gene alone does not appear to provide survival capacity of these cells in isolation. Both soluble and contact-mediated signaling mechanisms appear to be necessary for cell survival.

The reason is that apoptosis is the natural death of cells genetically determined

Dear P. Bagavandoss,

This problem is considered by me together with Elena Kadyshevich in the paper published in the journal "Global journal of science frontier research..." This paper is available in my and Elena's ResearchGate pages. The paper is rather long. If it, as a whole, is not interested for you, read pages 27-29.

The programmed death (apoptosis) evolutionarily fixed for living cells. Trigger to activate apoptosis is falling functional efficiency cells. The latent period for human RBC before switching apoptosis is 120 days, small animals - less. By the way, the population of nerve cells while maintaining an active intercellular signaling survives throughout a person's life. But it provided active mental activity. Otherwise, mechanisms are triggered apoptosis in the brain as well. Last remark. About immortal. Why is the program not included of the apoptosis in tumor cells? That would be meaningful if carried out research in this area with high efficiency, and then there is hope for a breakthrough in the fight against cancer.

No cell can live forever, if it does not die accidentally it will die naturally. The control mechanisms in the cells are to regulate activities such as mitosis (for example) in the somatic cells. If a cell is deviating from the rule of cell division, the control mechanism for this process releases a chemical signals to stop its further division, eventually send such a cell into a programmed cell death so as to prevent tumor formation, its spread and effects on other normal healthy cells.

In many cancer cells, expression of p53 or bcl-2 and other genes is changed. Thus, a balance beteen proliferation and cell death is also altered. Nevertheless, chemotherapy and radiotherapy trigger programmed cell death e.g. apoptosis in cancer cells

If we take the statment that apoptosis is the " natural" cell death and if one assumes that every living body shall die one day, this is the most natural way to do so. It could be trapped in some unknown way and this should be awsome! The problem is that to achieve the ever lasting cell we are talking about immortality...

Thanks to each n every researcher who helped me in learning new things which I don't know.

All the best in your investigation.