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: Understanding the Concept:
The question asks for the correct sequence of the major protein complexes of the mitochondrial electron transport chain (ETC). These complexes are typically numbered I through IV.
Step 2: Detailed Explanation:
Let's identify each complex listed:

B. NADH dehydrogenase is Complex I. It accepts electrons from NADH.
A. Succinate dehydrogenase is Complex II. It accepts electrons from succinate (via FADH₂). It is also part of the Krebs cycle.
D. Cytochrome bc1 complex is Complex III. It accepts electrons from Coenzyme Q (which gets them from Complex I and II).
C. Cytochrome c oxidase is Complex IV. It accepts electrons from cytochrome c (which gets them from Complex III) and transfers them to the final electron acceptor, oxygen.
The question asks for the sequence of the complexes themselves. They are conventionally ordered numerically from I to IV. Although Complex I and II operate in parallel, feeding electrons to Complex III, the standard listing of all four main complexes follows their numerical order. The correct sequence based on the complex numbers is I \(\rightarrow\) II \(\rightarrow\) III \(\rightarrow\) IV.
Translating this back to the given letters: I = B (NADH dehydrogenase) II = A (Succinate dehydrogenase) III = D (Cytochrome bc1 complex) IV = C (Cytochrome c oxidase) So the sequence is B, A, D, C.
Step 3: Final Answer:
The correct sequence of the complexes in their standard numerical order is B, A, D, C.