Question

Which is the terminal cytochrome which donates electrons to oxygen?

• A. $Cyt{a}_2$
• B. $Cyt{a}_3$
• C. Cyt b
• D. Cyt c

Answer 1

Answer: (B)

$Cyt{a}_3$

During electron transport system, NADH donates electrons to ubiquinone which then transfer it to cytochrome b. Cytochrome c gains electrons from cytochrome $b{c}_1$ of complex III and pass those to a binuclear copper center of complex IV. Complex IV has two hemes: cytochrome a and cytochrome $a_3$. The cytochrome $a_3$ is a component of binuclear copper center and accepts electrons from cytochrome a and transfer them to oxygen. So, cytochrome $a_3$ serves as terminal cytochrome. Thus, the correct answer is option B.