Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: 5holycows on 31/05/2012 20:22:50
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It seems very strange to me that humans cannot produce first class proteins, and so we have to get these elusive amino acids by eating animals that can... Is there a reason why humans can't, while e.g. cows can synthesise these proteins? Would it not be an evolutionary advantage if humans did not have biological pressures to constantly kill and eat other animals?
Thanks in advance, Ollie
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I also find it odd that there are a number of essential amino acids that humans can not produce.
However, until recently humans were unable to refine stuff like sugar. So, all food would be from the consumption of other cells which contain proteins.
Production of enzymes and cellular machinery to build amino acids would be energetically expensive, and unnecessary if those amino acids are readily available in the diet.
The typical bovine diet is different than the human diet, so the amino acid selection that they gain from their diet and bacterial flora may be different. Perhaps at some point we evolved to be carnivorous/omnivorous.
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Several years back I heard something about growing meat cells in big sheets in labs. But if people freak out about a genetically engineered potato, I'm guessing this idea wouldn't fly even if it worked.
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Vitamins = Vital Amines, ie ones we can't synthesise ourselves, and have to obtain from our diet.
In principle, it should be possible to genetically engineer gut bacteria which can synthesise vitamins for us.
- It would mean extra DNA which the bacterium has to maintain and copy every time it divides
- It's hard to see how a bacterium which carries on this extra task for our benefit would divide more quickly than one of it's siblings which doesn't have this overhead
- For bacteria, survival is all about divide and conquer!
- It's unclear how the bacterium would generate just the right amount of vitamin - not too little, and not too much (some vitamins become toxic if consumed to excess)
- It's beyond our current technology, but it is theoretically possible to insert the genes for vitamin production into human DNA. The level of expression would need to be regulated by feedback from the body systems which require each vitamin. It would be a complicated system.
- But would the extra overhead on human cells (which already support a fairly large genome) outweigh ease of obtaining these same vitamins through a balanced diet (or popping a pill)?
Even if we synthesised all our own vitamins, there are still many other essential dietary inputs that we should continue to obtain from our diet, like fixing atmospheric nitrogen into amino acids, converting carbon dioxide into sugar (photosynthesis), and collecting salt and minerals from the soil.