Azide, N_3^-, is a chemical compound with diverse uses, including as a preservat

Question

Azide, N_3^-, is a chemical compound with diverse uses, including as a preservative and as a propellant for airbag deployment. Azide inhibits the mitochondrial electron transport chain by binding to complex IV, cytochrome C oxidase, in the image at right. (Don't spend too long next to your airbag ellipsis) A. What are the substrates and products of the reaction carried out by complex IV? (3 substrates and 1 product ellipsis) B. If azide inhibits complex IV, will a cell be able to use oxygen during cellular respiration? C. (Possibly tricky) Will a cell whose electron transport chain that has been inhibited by azide be able to regenerate NAD^+? D. What part of the plasma membrane prevents H^+ ions from diffusing from the intermembrane space, across the membrane, and into the mitochondrial matrix? E. Is the process by which protons are moved from the matrix into the intermembrane space passive diffusion, facilitated transport, or active transport? Is this endergonic or exergonic? F. What type of membrane component is the enzyme cytochrome C oxidase (complex IV)? G. In which organelle is cytochrome C oxidase created, and what cellular structure creates cytochrome C oxidase? H. What is the function of the molecules NADH and FADH_2 in the electron transport chain?

Explanation / Answer

a) Substrates for complex IV: electrons, cytochrome c and molecular oxygen
Product: water

b) When complex IV is blocked, the electron transfer to the oxygen is also bloccked resulting in stopped aerobic respiration. Only, fermentation keeps the glycolysis going for short time.

c) A cells whose electron transport chain has been inhibited by azide can regenerate NAD+ using "alternate oxidase (alternative NADH dehydrogenase)" that transfers the electrons from NADH to molecular oxygen via ubiqionone.

d) The hydrophobic core of the plasma membrane prevents the diffusion of protons which are charged particlaes.

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