Corn lacks the essential amino acids isoleucine and lysine. beans lack the essential amino acids tryptophan and methionine. soy contains all the essential amino acids. why do many traditional diets combine corn (e. g., tortillas) with beans? a. to provide additional micronutrients b. to provide all the essential fats c. to provide all the essential amino acids d. to act as a multivitamin e. all of the above are reasons.