No Exit

Chuck Grimes cgrimes at tsoft.com
Fri Jul 14 09:09:37 PDT 2000


[happy to eat crow on my claims a few months back about the effects of gravity on cellular processes]

http://www.newscientist.com/news/news_224734.html

What a downer We may have to abandon our dreams of colonising space

``The skeletons within living cells may not form properly in zero gravity, say researchers in France. ...Physicists insisted this research wasn't worth doing, because gravity is too small, compared to electrostatic or thermal forces on molecules, to affect chemical reactions,' says Didier Schmitt, head of life sciences at ESA's European Space Technology and Research Centre in Noordwijk, the Netherlands. `This proves they were wrong.' [rest of article at link]'

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Ian,

What claims were those? I forgot or maybe missed them. For the sake of discussion, you can bring them up again or some change of mind. In any case this is interesting stuff.

Tubulin (microtubules) works in conjunction with actin (microfilaments) to form a Buckminister Fuller arrangement of struts and rubber bands inside the cell with the membrane as an outer skin. Both molecules are formed by polymerization which is controlled through GTP (tubulin) and ATP (actin).

These molecules are the mechanical equivalent of bones and muscles for cells. Basic cell motility is accomplished by elongation and shortening of pieces of this strut and band arrangement. Cell can extend pseudopods in some direct by extending the strut-band arrangement and creep with the membrane acting something like a tank tread on a surface. Alternately, in water, the membrane can be made to undulate through a similar changing configuration of the struts and bands.

More advanced structures like cilia are constructed with tubulin and actin. The filaments and tubes are aligned in an axial fashion to compose the individual cilia which act like tiny oars that are moved in a sweeping rhythm.

The role of gravitation in the formation and action of these molecules as been known for sometime in a general sort of way since gravity is required to accomplish some of these motions.

If you're interested in the detailed development of tubulin and actin and their role in structure and motility see, Molecular Biology of the Cell, Alberts et al, Garland, (latest edition).

Chuck Grimes



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