FADH2

Definition

FADH2 is a redox cofactor involved in cellular respiration, specifically functioning as an electron carrier in the citric acid cycle and oxidative phosphorylation. It is generated during the conversion of succinate to fumarate in the citric acid cycle, and plays a crucial role in the electron transport chain, where it donates electrons to facilitate ATP production through oxidative phosphorylation.

5 Must Know Facts For Your Next Test

1. FADH2 is produced from the reduction of flavin adenine dinucleotide (FAD) during specific steps of the citric acid cycle.
2. Each molecule of FADH2 generated yields approximately 1.5 ATP molecules when it donates its electrons to the electron transport chain, which is less than the 2.5 ATP from NADH.
3. In addition to being formed in the citric acid cycle, FADH2 can also be produced during beta-oxidation of fatty acids and in some amino acid catabolism.
4. FADH2 enters the electron transport chain at Complex II, bypassing Complex I, which affects its overall ATP yield compared to NADH.
5. The regeneration of FAD from FADH2 is critical for maintaining the balance of redox reactions within cellular metabolism.

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 donation initiates a series of reactions that lead to the pumping of protons across the inner mitochondrial membrane, creating a proton gradient. This gradient ultimately drives ATP synthesis through ATP synthase, though FADH2 yields approximately 1.5 ATP per molecule compared to 2.5 ATP from NADH, due to its entry point in the chain.
• Discuss the role of FADH2 in both the citric acid cycle and oxidative phosphorylation.
  • In the citric acid cycle, FADH2 is produced during the conversion of succinate to fumarate, acting as an important intermediate that captures energy from metabolic substrates. During oxidative phosphorylation, FADH2 transfers its electrons to the electron transport chain, which leads to ATP production via chemiosmosis. This dual role emphasizes its importance in both energy capture and energy conversion processes within cells.
• Evaluate how the presence of FADH2 impacts metabolic pathways and energy balance in cells.
  • The presence of FADH2 significantly impacts metabolic pathways by serving as a key electron carrier that links catabolic reactions to ATP generation. Its lower ATP yield compared to NADH influences cellular energy balance, guiding metabolic flux depending on substrate availability and energy demands. This dynamic relationship highlights how cells optimize their energy production strategies based on varying conditions and substrate types, ensuring efficient use of available resources for growth and maintenance.

Related terms

NADH: NADH is another important electron carrier that works alongside FADH2 in cellular respiration, providing electrons for the electron transport chain.

Oxidative Phosphorylation: This is the metabolic pathway where ATP is produced as a result of transferring electrons from NADH and FADH2 through the electron transport chain.

Citric Acid Cycle: A series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetyl-CoA, producing FADH2 and NADH.