or  a-ami*no acid  n :  any of the more than 20 amino acids that have an amino group in the alpha position with most having the general formula RCH(NH₂)COOH, that are synthesized in plant and animal tissues, that are considered the building blocks of proteins from which they can be obtained by hydrolysis, and that play an important role in metabolism, growth, maintenance, and repair of tissue .
 
 
 
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