Question

Cyanide is a deadly and notorious poison that inhibits the electron transport chain by competitively inhibiting cytochorome c oxidase.

Given this information answer the following questions:

Cyanide inhibition of the electron transport chain will __________ (simply state raise or lower) ATP production.

Cyanide inhibition of the electron transport chain will __________ (simply state raise or lower) NAD+ levels in the mitochondria.

Cyanide inhibition of the electron transport chain will __________ (simply state raise of lower) NADH levels in the mitochondria.

For part d. explain why.

Answer 1

• The mechanism of oxidative phosphorylation occurs in mitochondria of live cells.
• Electrons are transported across various components of electron transport chain (ETC), resulting in series of oxidation-reduction reactions within the membrane bound complexes in mitochondria (complex I, II, II, IV).
• Electrons are transported across various components of electron transport chain (ETC), resulting in series of oxidation-reduction reactions. NADH and FADH₂ are electron donors, their oxidation creates high concentration energy from electrons. This energy is used to pump proton from matrix to inter membrane space. Flow of protons creates and electrochemical gradient, which is used to generate ATP.

Answers:

a. Lowers ATP production

b. Lowers NAD+ levels

c. Raise NADH levels

d.

• Cyanide binds to complex IV in Electron transport chain.
• Cyanide ion interacts with the iron (Hem group) of the complex, acting as inhibitor of enzyme Cytochrome C Oxidase (aa₃).
• Thus, cyanide blocks the electron flow, redox reactions and there will be no proton motive force generated causing stopping of ATP production.
• Cyanide thus also prevent electron flow from electron donors like NADH and FADH₂.
• Thus, NADH cannot recycle to NAD+ resulting in increased NADH level and decreased NAD+ level.