Question

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

• 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 $a{a}_3\to O_2$ is $H+$ absorbing site
• D. $No{H}^{+}$is absorbed or released

Answer 1

Answer: (C)

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 acceped by $O_2$ and $H_{2}O$ is formed.