Potassium cyanide is a toxic substance that blocks the electron transport chain during cellular respiration. The image shows the outline of cellular respiration. Oxidative phosphorylation is blocked at the electron transport chain during cellular respiration. This results in the most of the A T P getting blocked and oxygen can't accept the electrons from N A D H. Which of the following represents a scenario of potassium cyanide toxicity? The substrate-level phosphorylation of glucose generates all the ATP required by the cell. Chemiosmosis still occurs in the inner mitochondrial membrane and generates all the ATP during cellular respiration. Oxidative phosphorylation that generates most of the ATP is blocked, and oxygen cannot accept the electrons from NADH. Electrons cannot be transferred from NAD to NADH, and ATP generation from both the substrate level and oxidative phosphorylation is blocked.