Posts Tagged ‘vesicula’

Membranas Vesiculares Fechadas: Nova evidência para Matrix/DNA Theory

terça-feira, janeiro 24th, 2012

O texto abaixo me fêz perceber que o aparecimento de vesiculas nas origens da Vida foi mera reprodução do “aparecimento” da aureóla de poeira estelar contendo um vórtice nas origens da galáxia. É o que chamam de “horizonte de eventos”. O tema suscita muitas questões, inclusive filosóficas e deixo-o aqui registrado para voltar quando o tempo permitir. O texto abaixo é de um post-comentário no artigo:

Can Science Define Life In Three Words?

http://www.science20.com/carl_zimmer/can_science_define_life_three_words-86052#comment-96222

xxx

Thor Russell ..
Thor Russell | 01/21/12 | 21:49 PM

OK I can’t pass up that kind of a challenge …Firstly what do you classify as life? Presumably a prion isn’t, a cellular virus is, what about a computer virus that can modify its own code?
Its not known how life began, but a definition of life must give sensible answers to different proposed processes. One I personally find interesting (compared to the replicator starting first) is that the boundary came first “closed, membrane vesicles” as they are called.

I can’t remember the steps in detail unfortunately but lets go with what i have, and you tell me exactly when chemistry becomes life.
1. The vesicles are essentially stable bubbles, made up of a phospholipid bilayer. These can form naturally, grow naturally in the right environment divide into two because of surface tension effects I think. Now as I said I don’t think it makes sense to make a binary on/off decision about what is life, because unless it starts suddenly it makes sense to describe the steps in terms of a progression. I would not call these vesicles alive, but label them as the beginning of a potential process from which it could start.

2. Vesicles that are porous enough to let long thin molecules through are more successful than those that don’t, because those molecules clump together when inside to give structure. These vesicles out-compete the other type. Alive or not?

3. Sometimes crystal-like molecules that can grow by themselves are assimilated into the vesicle. These provide more consistent structure than just random molecules. Vesicles that let these ones through specifically are more successful than those that just let anything through. The crystals and vesicles are now dependent on each other for their successful proliferation. This is looking a lot like “independent spontaneous cooperation” now isn’t it? Surely if you insist on this definition and a binary yes/no for life then this system is now alive.

However the system described is also clearly less life-like than a complete living cell with DNA. I argue that a clear yes/no answer for what is life is not possible or desirable and that your particular definition while definitely useful and thought provoking does not always give the correct answer.