User:Pyrrhus Adrian/Glycerol phosphate shuttle

The NADH generated during glycolysis in found in the cytoplasm and must be transported into the mitochondria to enter the oxidative phosphorylation pathway. However, the inner mitochondrial membrane is impermeable to NADH and NAD+ and does not contain a transport system for these electron carriers. Either the glycerol-3-phosphate shuttle pathway or the malate-aspartate shuttle pathway, depending on the tissue of the organism, must be taken to transport cytoplasmic NADH into the mitochondria.

These electrons bypass Complex I of the electron transport chain, making the glycerol-3-phosphate shuttle less energetically efficient compared to oxidation of NADH by Complex I.