Fadh2

Definition

FADH2 is a redox-active coenzyme that plays a vital role in cellular respiration, particularly in the citric acid cycle and oxidative phosphorylation. It serves as an electron carrier, transporting electrons to the electron transport chain, where its reduction potential helps drive ATP synthesis through the chemiosmotic mechanism. By accepting electrons from metabolic substrates, FADH2 contributes significantly to the production of energy within the cell.

5 Must Know Facts For Your Next Test

1. FADH2 is generated during specific steps of the citric acid cycle, such as when succinate is converted to fumarate by succinate dehydrogenase.
2. Each molecule of FADH2 that enters the electron transport chain can generate approximately 1.5 ATP molecules due to its entry point being at a lower energy level compared to NADH.
3. FADH2 donates its electrons directly to complex II of the electron transport chain, bypassing complex I, which reduces the overall ATP yield.
4. In addition to its role in aerobic respiration, FADH2 is also important in fatty acid metabolism and amino acid catabolism.
5. The regeneration of FAD from FADH2 occurs through reoxidation during various metabolic processes, allowing FAD to continue functioning as an essential coenzyme.

Review Questions

• How does FADH2 contribute to ATP production during cellular respiration?
  • FADH2 contributes to ATP production by donating electrons to the electron transport chain at complex II. This process leads to the establishment of a proton gradient across the inner mitochondrial membrane, which is crucial for driving ATP synthesis through ATP synthase. Since FADH2 enters at a lower energy level than NADH, it generates about 1.5 ATP per molecule compared to 2.5 ATP from NADH.
• Discuss the role of FADH2 in the citric acid cycle and its significance for overall energy metabolism.
  • In the citric acid cycle, FADH2 is produced during key reactions such as the conversion of succinate to fumarate. This process is significant because it allows for the capture of high-energy electrons that can be utilized later in oxidative phosphorylation for ATP synthesis. The production of FADH2 reflects the effective breakdown of carbon sources for energy, highlighting its importance in cellular respiration.
• Evaluate the impact of decreased FADH2 production on cellular energy metabolism and physiological functions.
  • Decreased FADH2 production can lead to diminished ATP generation since fewer electrons are available for the electron transport chain. This reduction in energy supply can impair vital physiological functions such as muscle contraction, nerve impulse transmission, and biosynthesis of essential biomolecules. Consequently, conditions that inhibit FADH2 production—like certain metabolic disorders—can severely affect overall cellular metabolism and organismal health.

Related terms

Flavin Adenine Dinucleotide (FAD): A coenzyme that exists in oxidized and reduced forms, FAD is involved in various metabolic reactions, including those in the citric acid cycle and fatty acid oxidation.

NADH:

NADH is another key electron carrier that, like FADH2, is produced during the breakdown of glucose and contributes to ATP production through oxidative phosphorylation.

ATP Synthase:

ATP Synthase is an enzyme that uses the proton gradient generated by the electron transport chain to synthesize ATP from ADP and inorganic phosphate.