Cyanide is an inhibitor of cytochrome c oxidase, the final electron acceptor of

Question

Cyanide is an inhibitor of cytochrome c oxidase, the final electron acceptor of the respiratory electron transport chain in the mitochondria. Its addition stops the production of ATP. Describe in 3 steps how the addition of cyanide will affect the membrane potential of a neuron. Respond in the space provided. 2 phrases per step only. Be explicit with your answers using concepts presented in the reading assignment and lecture. Step Zero - Addition of Cyanide and arrest of ATP production Step One Step Two Step Three

Explanation / Answer

Step 1: Elevation of cytosolic calcium

Deficiency of ATP leads slow but steady increase in cytosolic calcium.

This increase is due to the toxic release of intracellular calcium stores.

Step 2: Intracellular pH falls

Ionized calcium binds to negatively charged residues of proteins and competes with hydrogen ions for the same binding sites.

It may results in higher proton concentration and falls pH.

Step 3: Depolarization and change in membrane potential

Intracellular acidification or low pH causes depolarization.

The interior part of cell becomes less negative.

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