Question

What is the correct sequence of Transmembrane multiprotein complexes of the electron transport chain during respiration?
A. Succinate dehydrogenase
B. NADH dehydrogenase
C. Cytochrome c oxidase
D. Cytochrome bc1 complex
Choose the correct answer from the options given below:

• A. A, B, C, D
• B. A, C, B, D
• C. B, A, D, C
• D. C, B, D, A

Hint:

Memorize the names and numbers of the ETC complexes:

Complex I: NADH dehydrogenase
Complex II: Succinate dehydrogenase
Complex III: Cytochrome bc1
Complex IV: Cytochrome c oxidase
The electron flow path is I \(\rightarrow\) Q \(\rightarrow\) III \(\rightarrow\) Cyt c \(\rightarrow\) IV and II \(\rightarrow\) Q \(\rightarrow\) III \(\rightarrow\) Cyt c \(\rightarrow\) IV.

Answer 1

The Correct Option is C

Step 1: Concept Summary:
The problem requires identifying the correct sequence of the major protein complexes (I-IV) in the mitochondrial electron transport chain (ETC).
Step 2: Detailed Explanation:
Identifying each complex:

B. NADH dehydrogenase is Complex I and accepts electrons from NADH.
A. Succinate dehydrogenase is Complex II and accepts electrons from succinate (via FADH₂). It is also a component of the Krebs cycle.
D. Cytochrome bc1 complex is Complex III, receiving electrons from Coenzyme Q (from Complexes I and II).
C. Cytochrome c oxidase is Complex IV, accepting electrons from cytochrome c (from Complex III) before transferring them to oxygen.
The question asks for the standard sequence of these complexes, which is based on their numerical order: I \(\rightarrow\) II \(\rightarrow\) III \(\rightarrow\) IV. While Complexes I and II function in parallel, donating electrons to Complex III, the conventional listing follows the numerical sequence.
Therefore: I = B (NADH dehydrogenase) II = A (Succinate dehydrogenase) III = D (Cytochrome bc1 complex) IV = C (Cytochrome c oxidase)
The correct sequence is B, A, D, C.
Step 3: Final Answer:
The correct sequence of the complexes in standard numerical order is B, A, D, C.