A concept is presented relating the amino acid score of food proteins to experimental magnitude of biological value (BV). Integral and heterogenous parameters of BV might be expressed as a sum of two components: potential biological value (BVp) and coefficient of compensation (C). "BVp" (the first component of biological value), which depended on amino acid score of protein, is derived from Mitchell's principle involving the qualitative characteristics of food proteins. "C" (the second component of biological value) involved efficiency of the body in economy of deficient essential amino acids of food proteins during their catabolism. Some food proteins were considered using the concept developed. The best animal proteins (from milk and egg) proved to exhibit the highest magnitudes of "C", thus corroborating not only the hypothesis on presence of food proteins with alimentary specificity but demonstrating their distinct effect on protein-amino acid metabolism.