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As per intro-level biology: everything living is made of cells. Cells have their own life cycle - the cell cycle, and split into two via asexual reproduction when they get too big. So - what's all this got to do with you, the reader? I'd say everything - but that's cliche. Cells build us - and keep us alive, but what happens when cells don't do their job? When cells stick it to the man per-se?
Like others in this R.S.I.L series - take all my info here with a grain of salt. I currently study biology and have an alright working knowledge of these things, but am by no means an expert; I merely aim to give you all an introductory glimpse into the subject at hand. Enjoy the read - and I hope you all learn something helpful.
Part 1: Cell Mechanisms 101
If you all remember grade ~9 science class - you remember that cells have organelles like mitochondria - and at the center lies the nucleus. The nucleus stores a load of chromatin - a jumble of DNA and proteins which forms into chromosomes via mitosis. In mitosis (the splitting of 1 cell into 2) the chromatin turns into chromosomes which are then evenly divided among the two daughter cells. In human cells, it's 23 chromosomes per daughter cell (46 per mother cell), in dogs, it can be 39 chromosomes per daughter cells (78 per mother cell). But what makes chromatin and chromosomes so relevant to cell death?
Chromatin stores genetic information within cells - after all, it's essentially DNA. That genetic information often has a defined telomere in chromosome form - and telomeres are what control cell death. They act as an expiration date for each cell. Cell death (aka apoptosis) is normal, and can take more or less time depending on the type of cell. For instance: your epithelium (stomach lining) is essentially brand new every 3-6 days. Your skin replaces itself fully over 27 days. Muscle and bone cells, on the other hand - take much longer. So, telomeres act as an expiration date, which then signals apoptosis to your cells. Apoptosis allows new cells to grow in their place - and prevent excess growth. Question becomes: what happens when that expiration date comes on too soon, or too late? When cells 'stick it to the man' and refuse to die? That's where our other two main forms of cell death come in: necrosis and autophagy. Autophagy is another programmed cell death like apoptosis - but is used moreso in recycling of old cells. Anytime you're hungry and your body reuses fat cells as energy - that mechanism is helped via autophagy (fancy greek for self-devouring). Necrosis, on the other hand, is unplanned - and happens from a lack of nutrients or excess damage to cells.
Summary:
>Apoptosis is planned cell death which allows new cells to grow and reproduce efficiently.
>Autophagy is a planned, recycling form of cell death - a process to form old cells into something usable.
>Necrosis is unplanned cell death - when you die, your tissues decompose thanks to necrosis - they're not receiving any more nutrients. Lack of nutrients creates necrosis - among other things.
Part 2: Cancer & Cellular Disease
Cancer, by definition, creates out of control cells. A tumor is a growth of cells which refuses to listen to its expiration date - and splits uncontrollably. Without cell death, cells live too long, creating tumors, genetic mutations and therefore a host of issues (or benefits!). Here's a list of diseases / mutations which all have to do with the cell cycle.
>Cancer. I went over this one - but they're the perfect example of cells living past their expiration. Cell damage from environmental causes (or plain bad luck) creates a mutation within cells - potentially making them live longer than they're supposed to. At it's root, whether caused via environmental carcinogens, genetics, or others - cancer is caused by DNA damage. DNA contains these programmed codes which control apoptosis - carefully balancing cell growth with cell death. By damaging DNA, we throw off this natural balance - leading to too much cell growth, and uncontrollably low cell death - creating tumors and cancer cells. Paraneoplastic syndrome happens when your immune cells attempt to fight the few cancer cells it can detect via its immune system - as such, it's a rarer syndrome in cancer patients, as cancer typically goes undetected by your immune system. Summary: DNA damage is the main root of cancer, and since DNA controls your cells death, DNA damage can damage your cells' expected expiration date - making them reproduce out of control, forming tumors via carcinogenesis.
Carcinogenesis Flow Chart, Wikipedia:
>So, if cancer is caused via DNA damage, resulting in a LACK of cell death, what happens when there's too much cell death? When cells die too early for their expiration date? Necrosis. Rundown: necrosis in your brain (neurons) results in diseases like Alzheimer's or Parkinsons, among other brain damage. Necrosis in other places of your body can be result of autoimmune conditions - where your body attacks its own cells. Adds up - cells dying too early makes your immune system think there's some form of virus or disease in your system, but your white blood cells (T3, T4) have no proper viruses to attack - instead attacking normal, healthy cells - killing them and leaving their waste to gum up other cells' jobs, where that waste then triggers your white blood cells to further clean things up. The mechanism of necrosis in auto-immune conditions is a self-fulfilling, closed loop - it's where the 'auto' comes from.
>Technically - science has shown our ability to digest lactose as a genetic mutation - most animals don't feed themselves with other animals' milk, except for modern humans. Lactose intolerance is technically our normal, primal, un-mutated form, but by that modification to our lactase gene, we've managed to successfully digest dairy from other animals. Though it's not cancer, it's certainly derived from atypical cell cycle happenings - which result in mutations. Sum: Prolonged exposure to milk modified our DNA to allow better lactose digestion into adulthood by acting upon our childhood gene when we're being breastfed as babies. Metaphorically opening a door for milk into our adulthood via genetic mutation. It's not exactly one of the 3 forms of cell death; but I figured it was a neat way to end this off.
Part 3: Conclusion
That's cancer and cell disease 101 - I hope you guys learned something, and feel free to comment below any other suggestions you may have! I've done enough science-y RSIL blogs lately and need a new topic to spice things up.
Sources
>clevelandclinic.org
>Wikipedia
>NIH.gov
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