Substrate-level phosphorylation is the formation of ATP without the involvement of the electron transport chain. A phosphate group is added to each molecule of triose phosphate using inorganic phosphate from the cytoplasm. This forms two triose bisphosphate molecules. After a series of steps ATP is generated from the removal of the phosphate groups from each of the triose bisphosphate molecules. NAD is reduced by the hydrogen atoms released.The formation of ATP at the substrate level gives a net yield of 2 ATP (taking into account the 2ATP used at the start of glycolysis.) The product of the dephosphorylation and oxidation of triose phosphate is pyruvate.