Question

In the electron transport chain during terminal oxidation, which of the following cytochrome donates electrons to O${}_2$

• A. Cyto- b.
• B. Cyto- c.
• C. Cyto- $a_3$.
• D. Cyto- f.

Answer 1

The correct option is C Cyto- $a_3$.

Respiratory electron transport system is present in the inner mitochondrial membrane. The transfer of electrons between carrier proteins located in the inner mitochondrial membrane results in the simultaneous pumping of protons from inside the mitochondrial matrix to the peri mitochondrial space. The oxygen does not directly participate in the process of respiration except for the last step in mitochondrial electron transport system. The last electron carrier protein cytochrome a${}_3$ gives electrons to oxygen resulting in a reduction of oxygen to the water molecule.

So, the correct answer is option C