Question

Which of the following is true regarding the given electron transport chain?
$CoQ \rightarrow Cyt c \rightarrow Cyt aa _{3} \rightarrow O _{2}$

• A. $CoQ \rightarrow$ Cyt $c$ is $H ^{+}$absorbing site
• B. $aa _{3} \rightarrow O _{2}, H ^{+}$yielding site
• C. $CoQ \rightarrow$ Cyt $c$ is $H ^{+}$yielding site and $aa _{3} \rightarrow O _{2}$ 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 $N A D H^{+}$(received from Krebs cycle) is accepted by FAD as a result of which FAD is reduced to $F A D H^{+}$and $N A D H^{+}$is oxidised to $N A D$. Reduced $F A D H^{+}$is oxidised by $C O Q$, with the formation of $CoQH ^{+} . H^{+}$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.