Mitochondrial ETC — The cytochrome c oxidase complex (Complex IV) performs which set of functions during oxidative phosphorylation?

Introduction / Context:
Complex IV, cytochrome c oxidase, is the terminal enzyme of the mitochondrial electron transport chain. It couples the reduction of oxygen to water with proton translocation, strengthening the proton-motive force used by ATP synthase.

Given Data / Assumptions:

• Electron donor to Complex IV is reduced cytochrome c.
• O2 is the terminal electron acceptor in aerobic respiration.
• Proton pumping by Complex IV is part of chemiosmotic coupling.

Concept / Approach:
Evaluate each role: electron acceptance, oxygen reduction, and proton pumping. Complex IV accomplishes all three to complete the chain and maintain the gradient.

Step-by-Step Solution:

Verification / Alternative check:
Inhibitors like cyanide and carbon monoxide bind Complex IV and block both oxygen consumption and ATP production, demonstrating its roles.

Why Other Options Are Wrong:

Common Pitfalls:
Underestimating Complex IV’s proton pumping; remembering only Complexes I and III pump protons, but IV does as well.

Final Answer:
All of these.