E. which class of substances in model 2, polar or nonpolar, is more likely to be found in high concentrations in the bloodstream of a vertebrate? justify your reasoning.

Polar compound can't diffuse back to blood circulation after filtrated by kidney. This will cause more polar substance to be excreted in urine so nonpolar is more likely to be found high in concentrations. Only a few specific substance like glucose, ascorbic acid and vitamin B that is transported back by pump.