Fadh2

Definition

FADH2, or flavin adenine dinucleotide in its reduced form, is an important electron carrier involved in cellular respiration. It plays a crucial role in transferring electrons from metabolic substrates to the electron transport chain, ultimately contributing to ATP production. FADH2 is generated during specific metabolic pathways, notably the TCA cycle and the beta-oxidation of fatty acids, where it captures high-energy electrons that can be harnessed for energy production.

5 Must Know Facts For Your Next Test

1. FADH2 is produced during the TCA cycle specifically from the conversion of succinate to fumarate by the enzyme succinate dehydrogenase.
2. Each molecule of FADH2 can contribute to the synthesis of approximately 1.5 ATP through oxidative phosphorylation in the electron transport chain.
3. FADH2 differs from NADH in that it donates its electrons to Complex II of the electron transport chain, whereas NADH donates to Complex I.
4. FADH2 is also generated during beta-oxidation of fatty acids, playing a key role in energy extraction from fat metabolism.
5. Unlike NAD+, FAD can accept two electrons and two protons to become FADH2, making it a versatile cofactor for various redox reactions.

Review Questions

• How does FADH2 function within the electron transport chain and what is its contribution to ATP synthesis?
  • FADH2 functions as an electron carrier that delivers high-energy electrons to the electron transport chain. Once it donates its electrons at Complex II, these electrons continue through the chain, ultimately leading to the production of ATP. Because each FADH2 generates about 1.5 ATP compared to 2.5 ATP from NADH, it reflects different energy yield based on where it enters the chain.
• Discuss the importance of FADH2 in both glycolysis and the TCA cycle and how it impacts cellular metabolism.
  • FADH2 is not directly produced during glycolysis but is essential in metabolic processes such as the TCA cycle where it is formed from succinate oxidation. In contrast, glycolysis primarily generates NADH. The presence of FADH2 from the TCA cycle shows how interconnected metabolic pathways are, impacting overall cellular energy production by linking substrate breakdown with ATP generation.
• Evaluate how cofactor engineering could enhance the efficiency of metabolic pathways that involve FADH2 and what implications this might have for bioengineering applications.
  • Cofactor engineering aimed at optimizing FADH2 production could significantly enhance metabolic pathways like beta-oxidation and the TCA cycle. By modifying enzymes to improve FAD synthesis or its regeneration back to FAD, bioengineered systems could achieve higher yields of ATP and other valuable metabolites. This could have wide-reaching implications in synthetic biology, including biofuel production and creating more efficient microbial cell factories for bioprocesses.

Related terms

NADH: NADH, or nicotinamide adenine dinucleotide in its reduced form, is another key electron carrier similar to FADH2 that plays a significant role in energy metabolism.

Electron Transport Chain: A series of protein complexes located in the inner mitochondrial membrane that transfer electrons from carriers like FADH2 and NADH to oxygen, generating ATP.

TCA Cycle: Also known as the Krebs cycle, this series of reactions occurs in the mitochondria and generates FADH2, NADH, and GTP by oxidizing acetyl-CoA derived from carbohydrates, fats, and proteins.