The enzyme glutathione reductase replenishes the cell's supply of glutathione (gsh), regenerating two molecules of gsh from a single molecule of oxidized glutathione (gssg), using nadph as a source of two reducing equivalents. using standard reduction electrode potential data (provided on the biopchem. education website) and a typical cellular nadp+/nadph ratio of 0.005, calculate the equilibrium cellular concentration of gssg at ph 7 and 25oc, if the gsh concentration is 4 mm. [express your answer in units of picomolar, pm]