Question

Which cytochrome acts as a mobile electron carrier, transferring electrons between complex III and IV during ETS?

• A. Cytochrome a
• B. Cytochrome bc\({}_{1}\)
• C. Cytochrome c
• D. Cytochrome a\({}_{3}\)

Hint:

Complexes III and IV are fixed in the inner mitochondrial membrane, so a small loosely attached protein must carry electrons between them.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept
In the electron transport system (ETS), electrons pass through complexes I to IV placed in the inner mitochondrial membrane.
Some carriers are fixed in these complexes, while a few are small and mobile.

Step 2: Identify the carriers
Complex III contains cytochrome \(\text{bc}_{1}\) and complex IV contains cytochromes \(\text{a}\) and \(\text{a}_{3}\). All of these are fixed parts of the complexes.

Step 3: Find the mobile carrier
Cytochrome c is a small haem protein lying loosely on the outer face of the inner membrane.
It picks up electrons from complex III and hands them to complex IV, so it is the mobile carrier.

Final Answer:
The mobile carrier between complex III and complex IV is cytochrome c. \[ \boxed{\text{(C) }\text{Cytochrome c}} \]