Question

In the electron transport chain during terminal oxidation, the cytochrome, which donates electrons to $O_2$ is
(a)Cytochrome b
(b)Cytochrome c
(c)Cytochrome $a_3$
(d)Cytochrome f

Answer 1

Hint: During terminal oxidation, in the electron transport chain, a cytochrome that donates electrons to $O_2$ is present in complex IV. This domain transfers electrons and catalyzes the reaction of oxygen to water in this complex.

Complete answer:
The electron transport chain primarily takes place through many complexes of enzymes that are found in the mitochondrial membrane. Electrons are transferred to oxygen by the last cytochrome in the electron transport chain (cytochrome $a_3$ component of complex IV).
A chain of electron transport is a sequence of compounds that pass electrons through redox reactions. It takes place from electron donors to electron acceptors, and couples this electron transfer through a membrane with proton transfer. This creates a gradient of electrochemical protons that drives the synthesis of ATP. ETC's terminal cytochrome is Cytochrome $a_3$. It has both ${Fe}^{3+}$ and $C{u}^{2+}$. With ${Fe}^{3+}$, it picks up electrons and transfers electrons to oxygen by $C{u}^{2+}$.
So, the correct answer is, ‘Cytochrome $a_3$’.

Note: In the inner membrane of the mitochondria, the electron transport mechanism exists. The electron transport system mainly consists of six components organized in the NAD, FMN, cytochrome b, cytochrome c, cytochrome a, and cytochrome $a_3$ sequences.
The movement of electrons from inside the mitochondrial matrix to the peri mitochondrial space between the carrier proteins located in the inner mitochondrial membrane results in the simultaneous pumping of protons. Except for the last step in the mitochondrial electron transport mechanism, oxygen does not specifically participate in the respiration process. The last electron carrier protein cytochrome a3 gives oxygen to electrons, resulting in the oxygen reduction of the water molecule.