NADH vs. FADH2 — What's the Difference?
By Tayyaba Rehman — Published on December 18, 2023
NADH and FADH2 are electron carriers in cellular respiration, but NADH contributes more ATP than FADH2 during oxidative phosphorylation.
Difference Between NADH and FADH2
Table of Contents
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Key Differences
NADH and FADH2 are vital molecules in biochemistry, acting as electron carriers during cellular respiration. While NADH is formed primarily in glycolysis and the citric acid cycle, FADH2 is mainly formed in the citric acid cycle.
When considering energy production, NADH holds a slight advantage. During the process of oxidative phosphorylation, NADH can be used to produce more ATP compared to FADH2. This is because NADH starts the electron transport chain at a point that allows for the pumping of more protons.
Structurally, NADH and FADH2 are different. NADH is derived from niacin (vitamin B3) and stands for Nicotinamide Adenine Dinucleotide. On the other hand, FADH2 is derived from riboflavin (vitamin B2) and stands for Flavin Adenine Dinucleotide.
The cellular locations where NADH and FADH2 donate their electrons also differ. NADH donates its electrons to Complex I of the electron transport chain, while FADH2 donates its electrons to Complex II. This distinction in electron donation points contributes to their difference in ATP production.
Both NADH and FADH2 play crucial roles in maintaining the balance of cellular energy. While each has specific functions and characteristics, their combined efforts ensure efficient energy production within cells.
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Comparison Chart
Source of derivation
Derived from Niacin (Vitamin B3)
Derived from Riboflavin (Vitamin B2)
ATP production potential
Produces more ATP in ETC
Produces less ATP compared to NADH
Electron donation point
Donates to Complex I of ETC
Donates to Complex II of ETC
Full Form
Nicotinamide Adenine Dinucleotide
Flavin Adenine Dinucleotide
Primary Formation Location
Glycolysis & Citric Acid Cycle
Mainly in Citric Acid Cycle
Compare with Definitions
NADH
Derived from niacin or Vitamin B3.
Niacin, a crucial vitamin, plays a role in the formation of NADH in the body.
FADH2
An electron carrier primarily formed in the citric acid cycle.
The citric acid cycle generates energy-rich molecules, including FADH2.
NADH
An electron carrier formed during glycolysis and the citric acid cycle.
In the process of glycolysis, glucose is broken down, forming NADH in the process.
FADH2
Produces fewer ATP molecules compared to NADH during oxidative phosphorylation.
While essential, FADH2's contribution to ATP production is less compared to NADH.
NADH
Donates electrons to Complex I of the electron transport chain.
NADH starts the electron transport process by donating electrons to Complex I.
FADH2
Derived from riboflavin or Vitamin B2.
FADH2's formation in the body is linked to riboflavin, an important vitamin.
NADH
Produces more ATP compared to FADH2 during oxidative phosphorylation.
The electrons from NADH generate more ATP when they travel through the electron transport chain.
FADH2
Donates electrons to Complex II of the electron transport chain.
FADH2 bypasses Complex I and directly donates its electrons to Complex II.
NADH
A vital molecule in the balance of cellular energy.
For efficient energy production, the presence of NADH is essential.
FADH2
Essential for cellular energy production, though secondary to NADH.
FADH2, while not as potent as NADH, remains vital for cellular respiration.
NADH
The reduced form of NAD.
Common Curiosities
From which vitamin is FADH2 derived?
FADH2 is derived from riboflavin or Vitamin B2.
What's the full form of NADH?
NADH stands for Nicotinamide Adenine Dinucleotide.
Which molecule is derived from niacin?
NADH is derived from niacin.
Does FADH2 produce more ATP than NADH in the electron transport chain?
No, NADH produces more ATP than FADH2.
Does NADH donate electrons to Complex II?
No, NADH donates electrons to Complex I.
Which molecule, between NADH and FADH2, has a higher potential for ATP production?
NADH has a higher potential for ATP production.
Is FADH2 formed during glycolysis?
No, FADH2 is primarily formed during the citric acid cycle.
Which molecule contributes electrons at the beginning of the electron transport chain?
NADH contributes electrons at the beginning, specifically to Complex I.
Which molecule donates electrons to Complex II in the electron transport chain?
FADH2 donates electrons to Complex II.
Which molecule is associated with Vitamin B3?
NADH is associated with Vitamin B3 or niacin.
In which cellular process is NADH mainly formed?
NADH is mainly formed in glycolysis and the citric acid cycle.
Is FADH2 derived from Vitamin B1?
No, FADH2 is derived from Vitamin B2 or riboflavin.
Do both NADH and FADH2 act as electron carriers?
Yes, both NADH and FADH2 are electron carriers in cellular respiration.
Are both NADH and FADH2 crucial for the process of oxidative phosphorylation?
Yes, both NADH and FADH2 are vital for oxidative phosphorylation in cellular respiration.
What's the full form of FADH2?
FADH2 stands for Flavin Adenine Dinucleotide.
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Written by
Tayyaba RehmanTayyaba Rehman is a distinguished writer, currently serving as a primary contributor to askdifference.com. As a researcher in semantics and etymology, Tayyaba's passion for the complexity of languages and their distinctions has found a perfect home on the platform. Tayyaba delves into the intricacies of language, distinguishing between commonly confused words and phrases, thereby providing clarity for readers worldwide.
