• Question: why do people age?

    Asked by ollymursforever to Christine, Edd, Jess, Nicolas, Zara on 14 Jun 2011. This question was also asked by caarax15.
    • Photo: Edward Codling

      Edward Codling answered on 10 Jun 2011:

      This is one of the big unexplained problems in science – we don’t really know.

      Some scientists have suggested that we may be able to avoid the body degenerating as we get physically older – in theory our body could replenish itself indefinitely and we could live for (e.g.) 900 years or longer. Some jellyfish are actually thought to be immortal by doing this, while many other animals and plants live much longer than humans: http://www.bbc.co.uk/nature/12733853

      However, if we could stop people aging would it be a good thing? How would we deal with all the extra people in the world?

    • Photo: Jessica Chu

      Jessica Chu answered on 11 Jun 2011:

      Hi,

      Like what Ed has said, there are a lot of research going on in this area but it is still in the early stages so no one can give us a answer for that yet!

      I know very little about this area but I will try explain a few things that I think might be related?

      Everyone cells’ go through ageing! Things like free radicals (an atom or a group of atom that have loss one of its electrons so they are highly reactive and will react with anything in our body) can promote ageing as reported by some researchers.

      Natural processes that goes on inside our body such as enzyme reactions and phagocytosis (when white blood cells are getting rid of foreign molecules that enter our bodies) – these process as well as many more produces free radicals so it will have an impact on ageing!

      Free radicals can also be just present in the environment- UV light (sun), ozone, and air pollution (chemicals released from industrial sites). Another thing that will really increase the level of free radicals is by smoking.

      The term is Senescence is used to describe cells going through ageing. Not much is known- it could be coded in our genes (short lengths of DNA) and off-set at a certain time.
      Also, at the end of every chromosome (DNA that are packed in an ordered way) contain something that is called the telomere.
      Telomere is very important because it will shorten after every Mitosis (cell cycle which involves cell growing bigger, making a new copy of DNA and dividing to produce a new daughter cell). And when there is no more telomere left at the end of a chromosome, the DNA is no longer protected so it degrades- and the cell dies. The Hayflick limit is the number of division a cell can undergo before it stops so this will have some links with aging.

      Also Telomeres are very important in cancer research because the telomeres in cancer cells do not shorten!! So the cells keep on growing and dividing so it never dies! quite scary!
      Many scientists are trying to make drugs to target the telomerase (an enzyme that keeps on renewing the telomeres- adding more telomeres to the end of chromosome) because cancer cells are mutated to continuously make telomerase to renew itself. They are pretty clever cells!

      I hope this helps! 🙂

      I love google- if you are really curious maybe try googling the term ‘telomeres and ageing’ or ‘ free radicals and ageing’ – will probably get lots of interesting results!!

    • Photo: Zara Gladman

      Zara Gladman answered on 11 Jun 2011:

      Wow. That’s a really difficult question! One of the reasons we think people age has to do with cell division. Cell division allows the body to grow and repair itself – we need cell division to grow new blood, skin, bone… everything! However, the number of times cell division can happen in your body is fixed.

      In a cell, there is a nucleus or ‘brain’ which contains genetic code in the form of chromosomes, which are long strands of DNA. At the end of each chromosome is a piece of DNA called a telomere, which protects the chromosome. During cell division, the DNA in the chromosomes is copied but the telomeres, which do not contain any important code and are just there to protect the chromosome, are snipped. This means that every time a cell divides, the telomeres get shorter. A baby will have much longer telomeres than an adult! Eventually, the telomeres get so short that they can’t protect the chromosomes any more. Important parts of the DNA can become damaged and cells stop dividing.

      Do you remember Dolly the sheep? I saw her in a museum a few years ago! 🙂 She was the first mammal to be cloned from an adult cell. Most sheep live for 11 or 12 years but Dolly only lived to the age of 6. This is because she had shorter telomeres than other animals of the same age – she was biologically the same age as the old sheep she was cloned from.

      Other causes of ageing may include damage from ‘free radicals’ which harm mitochondria (mitochondria are found inside our cells and act as the cell ‘power plant’ by generating energy). This causes the cells to die. The environment and our lifestyle choices can also affect ageing – smoking, for example, can cause ageing of the skin and damage to tissues. Healthy living can help slow down many of the changes that the body goes through during ageing.

    • Photo: Nicolas Biber

      Nicolas Biber answered on 12 Jun 2011:

      Wow thanks Jess! I am glad someone was finally able to explain this to me so I understood it 🙂

      It’s been a long time since I have last done cell biology, so I do not really have an answer to the question about the cause of ageing. However, the question ‘why’ can also be answered by the purpose. If people – and all animals for that matter – didn’t age, they would never die, at least not of old age. But as Edd said they would still procreate, and there would just be more and more of them until the environment would not be able to sustain the population because what we call the carrying capacity would be exceeded. In a way it is in the interest of each species that its individuals die eventually, otherwise the species could not procreate, and without procreation there would be no evolution.
      For arguments sake we could assume that there once was a species whose individuals didn’t age and eventually die. The population of this species would grow and grow until their resources would be depleted and the species got extinct. Or the species would not procreate, the population size would remain the same, but there would be no offspring and therefore no evolution. Meanwhile a different species would age and die and therefore be able to evolve. The evolving species would eventually ‘out-evolve’ the species that has an eternal life but does not evolve and beat it in competition. The ‘eternal life’ species would get extinct again. Looking at it that way species that age and die have an advantage over species that do not.
      Did this help?

    • Photo: Christine Switzer

      Christine Switzer answered on 14 Jun 2011:

      This is a great question! Thanks especially to Jess and Zara for great explanations. I remember studying aging a little bit in biology class, and I remember a crazy word called apoptosis, which is described as programmed cell death. It’s a natural part of life in multi-cellular organisms. The cells seem to break into fragments and get absorbed by other cells. Cells in our bodies do this every day. I read somewhere that apoptosis is why we have fingers and toes instead of webbed feet! Apoptosis happens in the tissue between the fingers before we are born. As we age, the dynamics of this process change as well. Lots of scientists are studying apoptosis because they think it may explain some of the diseases that develop with age. Apoptosis gone wrong could be one of the triggers for cancer or diseases like multiple sclerosis (MS). We still have a lot to learn about aging.

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