X-Message-Number: 33055
Date: Fri, 12 Nov 2010 09:02:50 -0500
From: "Perry E. Metzger" <>
Subject: Holes
References: <>

> From: "Chris Manning" <>
> [snip]
> >> How can the robots even get into a cell without tearing a hole?  
> >
> > You clearly can't enter a cell without producing a hole in it --
> > cell membranes are not Klein bottles, so getting from the outside
> > to the inside requires a hole. The question is how you make a
> > hole that is either easily repaired or which self-seals. Again,
> > this has been considered before, in great detail. Freitas'
> > "Nanomedicine" is quite comprehensive.
> Nature must have solved this problem already, as water and
> nutrients pass into cells and wastes are removed. So - how does
> Nature do it? Can we imitate Nature, or even improve on it?

Small molecules travel directly across the membrane through small
pores in it. Some substances are actively transferred across the
membrane by mechanisms embedded in it, some travel purely via osmotic

None of these mechanisms will work for objects comparable in size to
organelles or the cell itself. On the other hand, natural systems
penetrate the membrane without permanently damaging it quite routinely
-- for example, viruses do this.

These are very easy to answer questions, easily answered by reading
basic biology textbooks.

In any case, I doubt that we will be imitating any of these mechanisms
in detail. They're all inappropriate.

Perry E. Metzger		

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