Question

Name the terminal acceptor of electrons in the electron transport chain.
A. Nitrate
B. Fumarate
C. Succinate
D. Oxygen

Answer 1

Hint: The mitochondrial electron transport chain consists of three large membrane-bound electronic carriers, flavoproteins (FMN, FAD), cytochromes and quinones (coenzyme Q, also known as ubiquinone because they are ubiquitous in biological systems). All of these electron carriers are located on the inner membrane of the mitochondria and together transfer electrons from donors such as $$NADH$$and $$FAD{H}_2$$ to acceptors .Electrons flow from charge carriers with more negative reduction potentials to electrons with positive reduction potentials and finally combine with final electron acceptor and H to form water.

Complete answer:
ETS is a sequence of carrier molecules capable of acting as an electron acceptor (or hydrogen acceptor) and an electron donor respectively, i.e. To undergo alternative reduction and oxidation. The ETS component is located on the inner membrane of mitochondria in eukaryotes and on the cytoplasmic membrane in prokaryotes. There are three classes of carrier molecules.
The first is flavoprotein which contains FMN (flavin mononucleotide) as a coenzyme. An example of this class is $$NAD{H}_2$$ dehydrogenase, which contains non-heme iron in addition to FMN. The function of this enzyme is to transfer hydrogen from $$NAD{H}_2$$ to ubiquinone.
 Ubiquinone or coenzyme Q is another class of carrier molecules which can absorb hydrogen atoms reversibly. It is a benzoquinone derivative with a long isoprenoid (R) chain.
The third and most important class of electron-carrying molecules consists of cytochromes. There are several different cytochromes, but not all of them in all organisms, but some members of this class are present in all aerobic organisms.
The final cytochrome ETS is cytochrome oxidase. It reacts with oxygen and transfers two electrons to oxygen to form a double negatively charged oxygen atom which combines with $$2H^{+}$$ to form a water molecule.

Hence, the correct answer is option (D).

Note: The enzymes of the electron transport system appear to be arranged in the membrane in such a way that the transfer of electrons must continue through the defined intermediate sequence. Energy changes occur during electronic transmission; The proton gradient and membrane potential are ultimately generated through the inner membrane. The proton gradient and membrane potential provide energy for ADP phosphorylation, a process known as oxidative phosphorylation.
The total yield of ATP is thirty eight moles per mole of glucose when the glucose is fully oxidized to $$CO2$$ and $$H2O$$.