If our body is constantly regenerating new cells, shouldn’t we technically stay the same forever? Why does aging even happen??
If our body is constantly regenerating new cells, shouldn’t we technically stay the same forever? Why does aging even happen??
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in a nutshell, our stem cells accumulate damage to their DNA that by themselves, are completely harmless – but over time compound to produce cells that are more likely to be dysfunctional, lack certain functions or simply can’t do things as efficiently 🙂
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Unfortunately, cells appear to be predisposed in a way to get worse and worse every time they copy themselves. The DNA has tips called telomeres, and they get shorter and shorter for every copy. When they get too short, the DNA unravels and can’t be used to make further copies. No one is completely sure why, especially since we know of cases in nature where this doesn’t happen thanks to perfect telomere maintenance.
Other reasons why we age is due to glucose binding, inhibiting DNA and further reducing cell replication. In case you needed further reason to avoid sugary food as much as possible.
Oxidative stress also impairs DNA. Sources like radiation and carcinogens can make it a lot worse.
Aging happens basically because every cell regeneration is a process that worsens over time for things that age. It’s never perfect consistently and only goes downhill as the process is replicated over and over and over and over and over and over.
After enough time symptoms begin to show, same as everyone.
I think it’s a great example of the concept of entropy. Second law of thermodynamics and all that.
At the xerox (copy) machine, ever try to make a copy of a copy? How about a copy of a copy, of a copy?
After many cycles the resulting image quality isn’t going to be great. Each time we copy, the results degrade a little bit.
The same thing happens to our cells. We don’t get perfect copies every time. Each subsequent copy is a little bit degraded.
Specifically, the ends of our chromosomes get a little bit shortened each time a copy is made. With time, the new cells don’t work as well as the originals, and we experience it as aging.
(For those too young for xerox machines… each time you re-save a jpeg, the re-compression degrades the image a little bit. Repeat this a bunch of times and you get a highly pixelated copy).
It is way more complicated than this, and I’m old so this is probably out of date, but:
Your cells have a few sources to look at when replicating, DNA which gives a broad collection of everything your cells can make, and methylation patterns which restrict or guide what will be made. With each replication, those methylation patterns change and replication slows down and errors occur. If methylation patterns didn’t change, you’d only ever have one cell type so we couldn’t do away with it.
It’s like how when someone copy-pastes a meme and the quality gets a little bit worse everytime. Or photocopying a photocopy of a photocopy. Eventually things get blurry, dna doesnt copy quite right, errors start to happen.
There are “sacrificial” parts in our DNA that get reduced over time when the cell divides. If they are used up, aging happens. The cells do indeed replace themselves, but the new one isn’t a completely identical copy.
Lobsters don’t have this issue, because they are able to regenerate these parts. In theory they are immortal and mostly die of causes like infections.
Humans, or basically all other animals don’t have that. We didn’t have any pressure to evolve such trait. Usually we are able to procreate before aging becomes a problem.
Take a copy of a copy of a copy … of a page enough times and eventually what you’re left with is a smudged mess.
This would be accumulating mistakes in the copying process.
Now imagine if every page also had a lot of whitespace at the edges that gets cropped off bit by bit with ever copy it. At first you’re just removing whitespace but eventually that whitespace will run out and you’ll be cutting off text.
This whitespace are Telomeres. Bit of DNA at the end of the strands that shorten every time the strand is copied.