Cell programmed to die, WHY?

[tempo]

Why does programmed cell death occur? Why do all cells have a death wish?

 

Out of interest, what happens when cells die?

 

The first 2 qns are cambridge interview qns

[RyanJ]

Why does programmed cell death occur? Why do all cells have a death wish?

 

Out of interest' date=' what happens when cells die?

 

The first 2 qns are cambridge interview qns[/quote']

 

Its a safety thing.

 

If a cell continues to reproduce then if somethign happens to go wrong with that cell then it will continue to reproduce indefinatly, in the case of the programmed cell it will die and that will be the end of it (Unless it evolves into a cancer).

 

Also, I think the cell becomes more suspetable to breakdowns of the DNA.

 

Cheers,

 

Ryan Jones

[LucidDreamer]

Programmed cell death is a reaction to environmental damage and the natural degradation of macro-molecules. Programmed cell death and a limited life span are the ways that life deals with environmental damage, degradation, and mutation. Without these things our existence would not be possible. Without them our earth would still host millions of immortal simple macro-molecules (assuming that abiogenises on earth is correct). Degradation of macromolecules is a natural occurrence that is related to entropy. Mutation is a necessary evil. An imperfect means of information storage and replication is the method that life deals with its hostile and changing environment and evolves into a more efficient and capable form, but with it comes the price of disease. Programmed cell death is a sacrifice of the few to ensure the survival and reproduction of the many. Without programmed cell death our bodies would be constantly plagued by disease, such as cancer, and unable to survive until we reproduce.

 

Check out these wikis: http://en.wikipedia.org/wiki/Programmed_cell_death

http://en.wikipedia.org/wiki/Apoptosis

[zyncod]

Apoptosis is an important part of neuron remodeling as well. Your ability to learn things hinges strongly on the ability of parts of your brain to die (and other parts to grow). Apoptosis is also used to prevent infections and cancers. What happens is a complex cascade but essentially, the cell releases proteases and DNAses that chew up proteins and the cell's genome, the nuclear membrane fragments, and the cell turns into little blebs of membranes that can be eaten by phagocytic cells.

[ecoli]

The first 2 qns are cambridge interview qns

 

Good luck on the interview... I had a friend who just got into Cambridge. I hear they're really tough and force you to think in abstract ways. If you can do that, then you should be fine.

[tempo]

Thanks for the answers.

 

Good luck on the interview... I had a friend who just got into Cambridge. I hear they're really tough and force you to think in abstract ways. If you can do that, then you should be fine.

[tempo]

Programmed cell death is a sacrifice of the few to ensure the survival and reproduction of the many.

 

Which are the few cells programmed to die i.e. how are they chosen?

[RyanJ]

Which are the few cells programmed to die i.e. how are they chosen?

 

Umm... they don't. All cells reproduce so many times and then die otherwise peopel would live forver

The first cell reproduces x times and then dies, the x daughter cells then reproduce x more times untill each of those die untill they all end up dead but no-one ever lives that long

 

Cheers,

 

Ryan Jones

[LucidDreamer]

Which are the few cells programmed to die i.e. how are they chosen?

I didn't mean it in the sense that some cells were preordained to die while others weren’t. I meant that some cells will experience problems, such as viruses, environmental damage, or problems in replication, that will cause them to commit suicide for the greater good of the colony. Or, as Zyncod pointed out, some neurons must die so that the brain can be wired for efficiency and specificity to the organism’s environment.

 

However, some kinds of cells do experience cell death more than others. Some cells don't suicide themselves unless they experience a certain trigger event (certain cells of the immune system) or environmental damage (neurons). Some cells go through mitosis frequently and die after a certain number of reproductions (epithelia cells). Some cells kill themselves early during development. Whether or not cells experience programmed cell death ultimately is determined from what kinds of cells they have become. Skin cells have a different life expectancy than liver cells. How they became liver cells or skin cells was determined by differentiation events. So whether a cell is likely to commit programmed cell death any time soon is determined first by what kind of cell it is, second by what stage of development the organism is in, and third by random environmental events (such as a virus infection).

[RyanJ]

I didn't mean it in the sense that some cells were preordained to die while others weren’t. I meant that some cells will experience problems, such as viruses, environmental damage, or problems in replication, that will cause them to commit suicide for the greater good of the colony. Or, as Zyncod pointed out, some neurons must die so that the brain can be wired for efficiency and specificity to the organism’s environment.

 

Good description there!

 

The cell suicide feature also releases a warning signal to the rest of the immune system, cancer cells should commit suicide but sometimes they don't leading to a cancer spreading.

 

Cheers,

 

Ryan Jones

[bascule]

Non-germ line cells die if it helps further the spread of the germ-line cells

[rakuenso]

if cells didn't die tadpoles wouldn't become frogs and we'd have webbed cancerous fingers

[Skye]

Which are the few cells programmed to die i.e. how are they chosen?

Apoptosis is often brought about within the cell by proteins called caspases. There are a variety of these that are activated in sequences under different circumstances. So you could say that apoptosis is caused by activating the caspase proteins (although there are other means, it is the most common).

 

You can divide how this happens into two categories, by signals from outside the cell (extrinsic pathway) and by signals from inside the cell (intrinsic pathway).

 

The extrinsic pathways are activated by the binding of ligand to a protein on the surface of the cell. An example is the Fas protein that binds to a corresponding Fas ligand that is expressed by T-cells and macrophages. An adaptor protein binds to the Fas protein on the inside of the cell, and then caspase proteins bind to these adaptor proteins, causing the caspases to be activated.

 

The intrinsic pathways are similar, but respond to something within the cytoplasm that shouldn't be there. An example is cytochrome c, which is normally within the mitochondria aiding in electron transport. If damage is done to the mitochondria the cytochrome c is released, and this binds to adaptor proteins, to which caspases bind and are activated.

 

In addition there are various ways these pathways are controlled, such as by inhibiting the caspases (preventing cell death) or by aiding the release of cytochrome c (accelerating cell death).

[ashennell]

Just to add -

 

the reason cells actually take an active roll in their own death is because it is an efficient, safe and fast process. That fast that it is a recently discovered process, relatively speaking. Apoptosis (programmed cell death) prevents cell contents from being leaked into the intercellular space, as would happen during cell lysis. This kind of leaking can cause problems for the surrounding cells as would be caused from physical tissue damage. There are other benifits of apoptosis as well. I think most of those have been covered already.

[muad'dib]

Another cause may be telomeres at the end of eukaryotic chromosomes. They are nucleotide sequences at the end of chromosomes that protect against degradation. There is an enzyme called telomerase that can lengthen the telomeres but unfortunately it isn't found in most cells of multicellular organisms like ourselves. This means that every time our cells divide our telomeres get shorter which means our DNA could eventually erode away because of replication. Telomerase has been found in cancer cells, meaning they can replicate forever without dying, which is pretty much what happens.