Question

Aerobic dehydrogenase in biological oxidation contains:

• A. NAD
• B. NADH
• C. NADP
• D. FMN \& FAD

Hint:

Aerobic dehydrogenases are flavoproteins containing FMN and FAD, crucial for transferring electrons in the electron transport chain.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Dehydrogenases are split into two groups based on whether they can react with molecular oxygen directly: aerobic dehydrogenases can, anaerobic ones cannot and must pass electrons along a transport chain instead.

Step 2: Key Fact:
Aerobic dehydrogenases carry flavin coenzymes, FMN and FAD, built into the enzyme itself. These flavins accept electrons from the substrate and then get reoxidized straight away by molecular oxygen, producing hydrogen peroxide as a byproduct.

Step 3: Detailed Explanation:
NAD and NADP are used by enzymes of glycolysis, the Krebs cycle, and biosynthetic pathways that need the electron transport chain or other acceptors, not oxygen directly.
NADH is only the reduced form NAD takes on after accepting electrons, so it is a product, not a coenzyme defining an enzyme class.
None of NAD, NADH, or NADP allow direct reaction with oxygen the way flavins do.

Step 4: Final Answer:
Aerobic dehydrogenases contain FMN and FAD as their coenzymes.