:NADH NAD+=NADPH(NADP Intermembrane space Inner Complex Ill membrane Complex I or pool Alternati xida Matrix NADH (NADT NADPH(NADP Figure 14.25 drial membrane. In addition to Complex I, plant mitochondria possess simpler on Rotenone-insensitive NADH and NADPH dehydrogenases of the inner mitochon membrane.These do not pump protons and are insensitive to Complex I inhi.> (single polypeptide) dehydrogenases on both surfaces of the mitochondrial inn bitors such as rotenone. Four dehydrogenases have been described, although not all of these may occur in all plant tissues. The two external dehydrogenases are thought to oxidize cytosolic NAD(P)H and feed electrons into the UQ pool. The two enzymes on the inner surface provide additional routes for oxidation of the NADH and NADPH formed in the matrix. The proteins involved in these pro- cesses have not yet been firmly identified Figure 4-6-0Figure 4-6-0