6.4: The Need for Amino Acids
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By 1900, researchers knew that proteins were actually made up of much smaller and more fundamental molecules—the amino acids. Soon afterwards, scientists found that life didn’t depend on protein per se, but on the amino acids of which it was composed. Indeed, we could get along very nicely without a single protein in our diet—if we consumed the amino acids that the proteins hold.
It’s actually quite possible to do so. Pure amino acids are readily available for purchase. But this plan would be quite expensive, and a jarful of amino acids is hardly appetizing fare.
The day may come when we move closer to eating this way. Algae, the one-celled animals which make green slime in ponds, are much more efficient than ordinary food crops in trapping solar energy and producing amino acids. So far, we’re happily stuck with the likes of the juicy roast of the Thanksgiving turkey, mashed potatoes, and pumpkin pie.
What a Few Amino Acids Can Do
Twenty different amino acids are needed to make protein (see Table 6-1 and Fig. 6-2)—11 of these we can make; the other 9 must come from our diet. The awesome fact about this handful of chemicals is that they can be juggled into the whole variety of plant and animal life on earth.
Consider how they’re used by our own bodies. Virtually all of life’s enzymes are made from them, as are enormous varieties of hormones and antibodies. More than this, they are the principal materials that make up our cells—cells of bone and brain, blood vessel, muscle, nerve, skin, intestine, gland, and lung. Our cells make a huge variety of proteins from these same 20 amino acids, not only to produce the chemicals of life processes, but also to repair and reproduce themselves.
Antibody: A protein that the body makes in response to a foreign substance, creating a defense and immunity against it (e.g., measles antibody made in response to a measles infection or vaccination).
Now reflect that we are only one species, and that these same amino acids are used still differently by other life forms—from mosquitoes to daffodils, from whales to sparrows, from fur and claw to leaf and bark. How is this possible?