• Question: why does your body age?

    Asked by rubii to Dalya, Derek, Sarah, Tim, Tom on 19 Jun 2011. This question was also asked by alliyia, emmagrace.
    • Photo: Tim Millar

      Tim Millar answered on 14 Jun 2011:

      We age because we are exposed to things in the environment like sun light, chemicals and gravity (just look at how long old peoples ears are!).

      There is also a limit to the amount of repair that the body can do after its been out in the sun for example. Normally our skin is very elastic because it has proteins in side it which allow it to rebound and stay firm and in place when strtched. As we get older, this ability is lost so things tend to get a little saggy.

      For other parts of the body their functio0n becomes limited with time of expose,. The lungs for example can be damaged by pollution and the repair process makes them less efficient. If you look around at elite athletes, most will have retired by the age of 35 and this is due in part to their natural loss of lung function.

      We also accumulate damage in our cells. As we replace old cells, we have to make new cells. We are all born with the information in our cells to be able to do this, but this copying process is not perfect. The longer we live the more mistakes thewre are in the new copies of cells. Eventually, there is so much damage in the cell that it dies and cannot be replaced. This is all part of the ageing process and why our life span is limited to an average around 80 years (although this is creeping up over time as we find ways to slow down the ageing process).

    • Photo: Sarah Thomas

      Sarah Thomas answered on 14 Jun 2011:

      Think about the cloning of Dolly the sheep. An adult sheep was cloned and a lamb was born that was an exact replica of the adult sheep. The had the same DNA. But when Dolly was only a few years old, she started to show signs or premature aging, and suffered from age-related diseases like arthiritis. She died at age 6 which is very young for a sheep. The reason for this is that Dolly’s DNA was old. As soon as you are born, your DNA starts to age. Every time a new cell is made, the DNA from the old cell is copied. Each time this happens, the DNA gets a little bit shorter!

      There is another reason for aging and this is called Free-radical theory. It is the idea that over your lifetime, your cells accumulate free radical damage. A lot of the biochemical reactions going on in your body produce free radicals and these are super reactive and there is evidence to suggest that these do damage to your body over time. The damage is called oxidative stress. This theory implies that antioxidants such as vitamins A, C and E slow the process of aging by mopping up these free radicals! But this theory is kind of out there and I don’t know how much evidence there is to support it….

    • Photo: Dalya Soond

      Dalya Soond answered on 14 Jun 2011:

      DNA is strung together on a long unit called a chromosome that will duplicate itself when the cell is dividing (rather than having each gene figuring out how to duplicate itself.)
      The enzymes that duplicate the chromosome cling onto the DNA. There is a little bit at the end (called a telomere) that can’t get duplicated… the enzyme would have no DNA to hold onto and would literally fall off the chromosome first. Telomere are also important for the 3D structure of the chromosome. Once you get past a certain number of divisions, the telomeres will get so short that they cannot give the chromosome the 3D structure it needs, and the cell will die.

    • Photo: Derek McKay-Bukowski

      Derek McKay-Bukowski answered on 14 Jun 2011:

      I’m pretty certain that you asked this from a biological perspective, but the ‘physics answer’ is that the dimension of time is directional. A property of the universe, known as entropy, dictates that systems will naturally result in an increased entropic state, as time goes forwards. Throw into this the concept of causality and, once grown up, it becomes difficult to sustain this statis and each event will cause some degree of degradation.

    • Photo: Tom Crick

      Tom Crick answered on 19 Jun 2011:

      I will answer this question in a similar way to Derek and use the arrow of time.

      The thermodynamic arrow of time is provided by the Second Law of Thermodynamics, which says that in an isolated system, entropy (a measure of disorder in a system) tends to increase with time.

      Maybe this is a good definition of ageing — your body is becoming more disordered!

Comments