Question: 91. The complex II of mitochondrial electron transport chain is also known as
(1) Cytochrome b c_{1}
(2) Succinate dehydrogenase
(3) Cytochrome c oxidase
(4) NADH dehydrogenase
Answer: Option (2)
Explanation:
The mitochondrial electron transport chain consists of four main complexes embedded in the inner mitochondrial membrane.
Complex I is known as NADH dehydrogenase, which accepts electrons from NADH.
Complex II is known as succinate dehydrogenase, which is the same enzyme that participates in the Krebs cycle.
Succinate dehydrogenase catalyzes the oxidation of succinate to fumarate and transfers the electrons to FAD, forming FADH_2.
The electrons from FADH_2 are then passed directly to coenzyme Q in the electron transport chain.
Complex II does not pump protons across the mitochondrial membrane, unlike Complex I, III, and IV.
Hence, Complex II of the mitochondrial electron transport chain is correctly identified as succinate dehydrogenase.