Question

What is the function of coenzyme Q?

Answer 1

Hint: Coenzyme Q is also known as ubiquinone plays a major role in energy metabolism. It is present in the process of chemiosmotic ATP synthesis.

Complete answer:
Coenzyme Q is the pathway of joining the route of FMN and FAD from where the electron enters the mitochondrial electron transport chain. This enzyme is used in Chemiosmotic ATP synthesis. Let us study about that:
Certain electron carrier molecules in the mitochondrial ETS are "pure" electron carriers and do not carry hydrogen ions or protons. These are called non hydrogen carriers, and include the cytochromes and iron-sulphur proteins. Other electron carrier molecules carry hydrogen atoms, that is proton as well as electron. These are called hydrogen carriers, and include FMN, FAD and coenzyme Q.
In the first step of ETS, NADH transfers its electron pair and $H^+$ ion to FMN and becomes NAD. Because FMN can carry two $H^+$ ions and two electrons, it draws one additional $H^+$ ion from the mitochondrial matrix and changes to its reduced form from $FMNH_2$. The latter transfers its electron pair to the next carrier molecule of the ETS, the iron-sulphur protein. The fe-S protein then transfers the electron pair to coenzyme Q. The coenzyme Q is a dual hydrogen electron carrier. It draws a pair of $H^+$ ions from the mitochondrial matrix to change into the reduced form, COQH2. COQH2 then transfers its electron pair to the next carrier molecules of ETS, the cytochromes are pure electron carriers COQH2, on oxidation to CoQ, release its two $H^+$ ions into the intermembrane space.

Note:
Coenzyme Q was first described as a mobile diffusion component localized between complexes. Due to its extremely hydrophobic nature, Coenzyme Q is localized in the hydrocarbon interior of the lipid bilayer of the inner mitochondrial membrane. Diffusion here takes place at a very high rate. The best- known mechanism is the Q-cycle was first proposed by the Nobel Laureate Peter Mitchell.