Transmembrane movement of reducing equivalents occurs under aerobic conditions. extramitochondrial nadh produced by glycolysis must be oxidized by the mitochondrial electron-transfer chain. consider a preparation of rat hepatocytes containing mitochondria and all the cytosolic enzymes. if [4-3h] nadh is introduced, radioactivity soon appears in the mitochondrial matrix. however, if [7-14c] nadh is introduced, no radioactivity appears in the matrix. how are these observations consistent with what is known about the permeability of the inner mitochondrial membrane and the malate-asparate shuttle? how exactly do the 3h get back into a standard electron carrier? (hint: see slides from lec10, focus on the "front end" of the malate-aspartate shuttle).