Question

How does the location of the electron transport chain differ in eukaryotes and prokaryotes?

Answer 1

Hint: ETC or electron transport chain consists of a chain of complexes that perform the function of transferring electrons from electron donors to acceptors. This transfer includes redox reactions and simultaneous transfer of protons across the membrane. This transfer of electrons is a type of exergonic process.

Complete answer:
Electron transport chain in case of eukaryotes is present in the inner membrane of mitochondria. Electrons enter the transport chain from the molecules of $NADH$ and $FAD{{H}_{2}}$ which are earlier produced. $NADH$ converts into $NA{{D}^{+}}$ and the released electrons move through complex I and this leads to pumping of protons from matrix to intermembrane space. $FAD{{H}_{2}}$ also donates electrons to complex I but it doesn’t lead to the pumping of electrons. From complex, I and II electrons are transported to an electron carrier known as ubiquinone which reduces to $Q{{H}_{2}}$ and transfers an electron to complex III.

During the movement of electrons in complex III, protons are pumped across the membrane. Then electrons are transferred to cytochrome c which is a mobile carrier and then to complex IV which leads to the pumping of protons across the membrane. From Complex IV electrons are transferred to ${{O}_{2}}$ which leads to splitting of the molecule into two two oxygen atoms and after accepting protons from the matrix, two molecules of water are formed.

Electron transport chain in prokaryotes is present in the plasma membrane and is as follows:
$NADH\to $Complex I$\to Q\to $Complex III$\to $Cytochrome C$\to $Complex IV$\to $${{O}_{2}}$
 (Proton pumps are depicted by complex I, III and IV, electron carriers are depicted by Q and cytochrome C and electron acceptor is depicted by ${{O}_{2}}$)

There are many electron acceptors and donors in case of the prokaryotic electron transport chain and NADH is the most important electron donor.

Note: Electron transport chain is present in prokaryotes in the plasma membrane and eukaryotes in the inner membrane of mitochondria. Two main functions of the electron transport chain include the production of proton gradient and regeneration of electron carriers.