Question

Which of the following is true regarding the given electron transport chain?
CoQ$\to$ Cyt c$\to$ Cyt $a{a}_3\to O_2$

• A. CoQ$\to$ Cyt c is $H^{+}$ absorbing site
• B. $a{a}_3\to O_2,H^{+}$ yielding site
• C. CoQ$\to$ Cyt c is $H^{+}$ yielding site and $a{a}_2\to O_2$ is $H^{+}$ absorbing site
• D. No $H^{+}$ is absorbed or released.

Answer 1

Answer: (C)

CoQ$\to$ Cyt c is $H^{+}$ yielding site and $a{a}_2\to O_2$ is $H^{+}$ absorbing site

In electron transport chain, electrons transport through a series of carriers. $H^{+}$ of $NAD{H}^{+}$(received from Krebs cycle) is accepted by FAD as a result of which FAD is reduced to $FAD{H}^{+}$ and $NAD{H}^{+}$ is oxidised to NAD. Reduced $FAD{H}^{+}$ is oxidised by CoQ, with the formation of $CoQ{H}^{+},H^{+}$ ions then move to Cyt b, then Cyt c, Cyt a and Cyt $a{a}_3$. Ultimately these $H^{+}$ are accepted by $O_2$ and $H_{2}O$ is formed.