The cells within their small intestine are «open» (they have spaces between them) which allows whole proteins and pathogens (amongst other macromolecules) to get into their bloodstream and basically create havoc within their little digestive systems! (themilkmeg.com)
This means that proteins can self - regulate or be regulated by other macromolecules without the need for proximity. (nimbios.org)
While at BTI Laura worked with scientists and educators to designed lab activities and lessons to introduce students to proteins, carbohydrates, fats and other macromolecules while teaching about biofuels. (btiscience.org)