The numbers game

By Vic Arcus 16/02/2010 4


Biology is about big and small. Really big (a whale) and really, really small (a bacterial cell). For a beautiful visual tour of the big to the very small, I can recommend this from the Learn Genetics website (this website was recently awarded the Science prize for online resources in education). This animated web page lets you zoom from a coffee bean down to a virus and a protein. To get with the jargon its an “order-of-magnitude” thing. Like all jargon, this is a fancy way of saying something simple. Two numbers differ by an order of magnitude if one is ten times bigger or smaller than the other – its just the number of zeros before or after the “1”. For example, 1 meter is 2 orders of magnitude larger than 1 cm (1 m = 100 cm). A blue whale is about 30 m long. A bacterial cell has a diameter of about 1 micrometer! All in all, life on our planet covers 7 orders of magnitude – a blue whale is 7 orders of magnitude bigger than a bacterium (30 m = 30,000,000 micrometers)!

For big and small biological numbers, many orders of magnitude apart (and for the geeks amongst us), there are a plethora of interesting and wacky examples at B1ONUMBERS. There are icky numbers – there are 10 times as many bacterial cells in your body compared to your own cells. There are practical numbers – ordinary “white collar” work requires about 8,000,000 Joules of energy per day (about 1,910,000 calories). There are environmental numbers – the average turnover of plant organic matter on land is 19 years. There are amazing numbers: An E. coli bacterium must consume 2,000,000,000 molecules of glucose before it can divide in two! For the skeptics, B1ONUMBERS provides you with the original reference and you can find out exactly how the scientists arrived at that particular value. And for the rigorous, the authors at B1ONUMBERS have written great paper on “A feeling for numbers in biology“.

In an earlier post, I talked about the ribosome which is the molecular machine that translates the information on DNA and RNA to manufacture proteins in our bodies. How fast can it do this? B1ONUMBERS says… ~16 amino acids per second! How often does the ribosome make a mistake? About once every 5 thousand amino acids!


4 Responses to “The numbers game”

  • Hi Vic
    Great blog – most entertaining – that I’ve only just discovered although I now can’t remember how … hopefully I”ll find my way back and pass it on to Meg and a few others.

    Cheers
    Chrys

  • Hi Vic

    Cool post, thanks. I found my way to your blog via Chrys.

    Scale is a great mindbender. My particular brand of biology (algae) is fairly subject to it, since there are so many unicellular species and also some huge ones like Macrocystis seaweeds (up to 100 m long or so). Yet they are mostly interrelated via ancient unicells, with various lineages exploring the “drunkards walk” into macroscopic size ranges independently.

    Nonetheless I’m going to try and be interesting and argue about your first sentence. (Can’t let the climatologists have ALL the controversy!) I reckon biology is the study of the mid-range. The study of the big and small is physics, where you have scales at which relativity actually matters (in the words of an engineering friend): masses large enough to exert major deformations on spacetime, bending light and whatnot, versus subatomic scales in quantum mechanics, and many physicists apparently spending their lives trying to reconcile the two…

    I reckon something that people often forget scale-wise is that we are a really big species, right at the top end of biological scale. I mean there is the occasional iconic bit of megafauna but actually well over 99% of species must be smaller than us. There are or have been big animals (especially when oxygen levels were historically higher), but I suspect that the huge majority of tetrapods and other fish have always been small and nervous – to say nothing of invertebrates. Then there are the plants, which are really a branch of algae, with the greatest genetic diversity occurring among the microbial ones. Someone else has made this point and I can’t remember who so apologies to whoever it is for lack of acknowledgment.

    This also reminds me of a conversation I had with an ecologist once, who was pretty mathematically minded, and liked looking for fractals in biology. He said it was tempting to view a tree as being a collection of chloroplasts, though he preferred to see it as a collection of cells since that gave him the opportunity to make general statements about carbon and nitrogen in a way that made scale a bit irrelevant.

    The last thing your post brought to mind was the beginnings of what seems to be getting called “quantum biology”. I’ve seen papers describing both protein evolution and photosynthesis in which quantum mechanics has been invoked (the Copenhagen Interpretation style involving indeterminate quantum states). It all looks a bit shaky to me, especially the first one, but I wonder if this research area is likely to grow? Any comments from a protein biochemist? It sounds like the sort of thing Schroedinger (or maybe Dirk Gently – “at the quantum level and therefore at all levels”) would have done if he’d been a biologist and less sceptical – finding ways quantum mechanics might actually influence our experience of the world at our scale. I suppose you could apply the many-worlds idea to biology in the same (shaky?) way.

    Anyway sorry for this long and rambling comment. Do I sounds like a nutcase? I don’t often comment on blogs. Thanks for a stimulating post

    Phil