I'm sure that there are many religious explanations for this, but I'm looking for a biological one. If cells keep on replicating themselves, why don't organs, muscles and other things stay the same? Why would they get weak? I understand why skin would get wrinkly, and not stay smooth, but not about other body parts.
P.S. I'm not looking for emotional support here(I'm not old), I'm just curious.
2007-03-23 02:06:00 · 2 answers · asked by Ory O Oreo 3 in Science & Mathematics ➔ Biology
Aging is biologically referred to as senescence, so you can probably find some good articles with that.
One theory that I learned in cellular biology (Telomeric Shortening Theory) is that DNA shortens over the lifespan... so in effect, the telomeres* shorten each time that a cell replicates to divide. This is because DNA is uneven on the ends and when it replicates, it can't replicate everything to the end of the strand. The final nucleotides are dropped, resulting in a gradual shortening throughout ones lifespan (as each human comes from one cell). Loss of genetic material would eventually lead to cells becoming worn and working together less efficiently until death by some mechanism occurs.
*telomeres - on the end of every chromosome, we have highly repetitive DNA that doesn't code for anything.
Gametocytes (which divide by mitosis to create sperm and eggs... basically they're a kind of cell in the testes and ovaries) have telomeric lengthening mechanisms so that each new human being starts out with long telomeres.
Another theory is that aging is evolutionarily advantageous, the goal of any species being to proliferate and continue the survival of their genes, not necessarily the individual (The Disposable Soma Theory). The most likely way to ensure that genes are passed on is through reproduction, so that each chid will have some of your genes. Evolutionarily then, it has become more advantageous all along the way for organisms to invest in reproductive success early on so that they have a better chance at reproducing quicker, even though it means senescence and death later on rather than individual success. Even if an organism is 'immortal', the chances of survival decrease with age as accidents, predation (as predators evolve to be better capable of chasing you down and killing you), and disease (as diseases evolve, possibly faster than your immune system can, not to mention body systems slowing down and losing function) all become more likely to take your life. Tied to this is apoptosis, that cells are programmed to die as soon as a genetic defect inhibits certain genes in the cell so that the cell doesn't multiply as cancer would.
2007-03-23 02:29:38 · answer #1 · answered by ndrw3987 3 · 0⤊ 0⤋
Biologically, things simply wear out. Think about your body's repair mechanisms. Statistically, the longer they are in operation the higher the probability that something will go wrong (an imperfect repair).
I have also heard the telomere theory (that eukaryotic chromosome telomeres degrade slowly over time, an actual biological clock/timer). There is no single known cause for aging. What is known are bits and pieces of why things fail to function perfectly all the time and forever.
2007-03-23 03:27:20 · answer #2 · answered by Shanna J 4 · 0⤊ 0⤋
I suppose everything begins and comes to an end...Even the
galaxies get born and die, it's in a nature of matter itself...
Complex matter which forms human body is highly unstable, it is furthermore subject to decomposition due to structure of organic ( and non - organic ) systems in human body...It is possible to support life functions artificially for some time ( that's what medicine really is doing ! ), but finally death is inevitable...
2007-03-23 02:15:30 · answer #3 · answered by javornik1270 6 · 0⤊ 0⤋
According to certain laws of the universe, all things tend toward a state of decay and disorder. It's entropy, a fundamental reality of all ordered systems. Entropy is disorder, and all things once ordered begin their journey toward greater entropy. That's why you constantly need to fight the battle against entropy to survive. Even daily, don't brush your teeth, they will decay.
In laymen's terms, the laws of entropy say you can never win and you can never stay ahead.
2007-03-23 03:41:28 · answer #4 · answered by Anonymous · 0⤊ 0⤋
There are two ideas behind this:
(i)Oxygen free radicals are toxic and are short of one electrons. So as they accumulate in the cells they cause damage to DNA membranes and cause all its contents to leak out. So the cell is damaged.
(ii) Programmed cell death: As with bacteria, it has been discovered that bacterial cells are genetically programmed to die.
2007-03-23 02:36:20 · answer #5 · answered by Anonymous · 0⤊ 0⤋