[OT] Short sci-fi story: The Lifeboat

Originally posted by geoschmo:
My actual knowledge isn't any more then yours, but my best guess would cause me to be a little more optimistic. Our bodies don't really need specific types of plant and animal matter afterall. Our digestive system breaks those down into the basic nutrient blocks that our body does need. And those basic nutrients should be pretty much the same, despite being combined in radically different ways. Of course our survivors would probably need a chemist or botanist and some laboratory equipment to be able to determine what is safe to eat and what's not. Since we wouldn't have millions of years of common memory to rely on.

Caveat: My understanding is also based on pop-science and sci-fi, but here goes...

Our digestive systems break food down by enzyme action. It's not enough that a molecule be composed of the right number of atoms of Carbon, Oxygen and Hydrogen, they also have to be the right shape for the enzyme to be able to "fit" and catalyse a reaction. For example, it's possible to make sugars whose molecules are the mirror-image of the shape of "normal" sugars, and these manufactured sugars will pass straight through the system without being digested because our sugar enzymes don't match them.

And supposing we can digest the alien plants (or animals)? Humans digest proteins by breaking them down into their component amino acids, absorbing them into the bloodstream, and then re-assembling them into the proteins we need. But we need a particular balance of IIRC eight key amino acids, in the right proportion. It's possible for example for a badly chosen vegetarian diet to contain lots of protein, but for the protein to be nutrionally useless because key amino acids are missing or in short supply.

Given how many possible combinations of protein and polysacharride (it's a long time since I've had to spell that...) there are, it's hard NOT to image a carbon-and-water based alien bio-chemical ecosystem that's like ours, but not like ours enough to be edible (or at least, nutritious when eaten...)

Mark