 Proteins were recognized as a distinct class of biological molecules in the eighteenth century by Antoine Fourcroy and others , distinguished by the molecules ' ability to coagulate or flocculate under treatments with heat or acid . Noted examples at the time included albumin from egg whites , blood serum albumin , fibrin , and wheat gluten . 
 Proteins <a href='uninflect' title='1'><mark>were</mark></a> recognized as a distinct class of biological molecules in the eighteenth century by Antoine Fourcroy and others , distinguished by the molecules <a href='null_genetive' title='2'><mark>'</mark></a>ability to coagulate or flocculate under treatments with heat or acid . Noted examples at the time included albumin from egg whites , blood serum albumin , fibrin , and wheat gluten . 
Proteins was recognized as a distinct class of biological molecules in the eighteenth century by Antoine Fourcroy and others , distinguished by the molecules  ability to coagulate or flocculate under treatments wit heat or acid . Noted examples at the time included albumin from egg whites , blood serum albumin , fibrin , and wheat gluten .