The process of transferring reducing equivalents from the cytosol into the mitochondria; NADH is used to synthesize glycerol 3-phosphate in the cytosol; this compound is then transported into the mitochondria where it is converted to dihydroxyacetone phosphate (DHAP) using FAD; DHAP then returns to the cytosol to complete the cycle. [ GOC:jl http://www.ncbi.nlm.nih.gov/pubmed/16368075 GOC:mtg_electron_transport https://www.worldcat.org/search?q=bn%3A0716720094 ]