FADH2

Definition

FADH2 is a redox cofactor that is involved in several metabolic reactions, functioning as an electron carrier in cellular respiration. It plays a critical role in the electron transport chain, where it contributes to the generation of ATP by donating electrons, ultimately leading to the production of energy necessary for cellular functions. As a reduced form of flavin adenine dinucleotide (FAD), FADH2 is generated during metabolic processes such as the Krebs cycle and fatty acid oxidation.

5 Must Know Facts For Your Next Test

1. FADH2 is produced during the Krebs cycle when succinate is converted into fumarate by the enzyme succinate dehydrogenase.
2. In terms of energy yield, each FADH2 molecule can generate about 1.5 ATP molecules when oxidized in the electron transport chain.
3. Unlike NADH, which donates electrons to Complex I of the electron transport chain, FADH2 donates electrons to Complex II, leading to a lower ATP yield.
4. FADH2 also plays a role in fatty acid metabolism by participating in the beta-oxidation process, which breaks down fatty acids into acetyl-CoA units.
5. The reoxidation of FADH2 back to FAD occurs at the electron transport chain, facilitating the continuation of cellular respiration and energy production.

Review Questions

• Explain how FADH2 contributes to ATP production during cellular respiration.
  • FADH2 contributes to ATP production by donating electrons to the electron transport chain at Complex II. This transfer initiates a series of redox reactions that pump protons across the inner mitochondrial membrane, creating a proton gradient. The potential energy from this gradient is then used by ATP synthase to generate ATP as protons flow back into the mitochondrial matrix.
• Compare and contrast FADH2 and NADH in terms of their roles and energy yields in metabolic pathways.
  • FADH2 and NADH both serve as important electron carriers in metabolism, but they differ in their roles within the electron transport chain. While NADH donates electrons at Complex I and yields approximately 2.5 ATP per molecule, FADH2 donates at Complex II and yields about 1.5 ATP. This difference in energy yield stems from their points of entry into the electron transport chain and the subsequent proton pumping efficiency.
• Evaluate the importance of FADH2 in both the Krebs cycle and fatty acid oxidation, discussing its impact on overall metabolic efficiency.
  • FADH2 is essential in both the Krebs cycle and fatty acid oxidation as it captures high-energy electrons that drive ATP synthesis. In the Krebs cycle, FADH2 is produced during key steps like succinate oxidation, contributing to energy output. In fatty acid oxidation, it facilitates efficient breakdown of fats into usable energy forms. The production and reoxidation of FADH2 enhances overall metabolic efficiency by enabling continuous ATP generation from various substrates.

Related terms

NADH: NADH is another key electron carrier in metabolism, similar to FADH2, that plays a crucial role in energy production during cellular respiration.

Krebs Cycle: The Krebs cycle, also known as the citric acid cycle, is a series of enzymatic reactions that produce energy through the oxidation of acetyl-CoA, resulting in the formation of FADH2 and NADH.

Electron Transport Chain: The electron transport chain is a series of protein complexes in the inner mitochondrial membrane that transfer electrons from electron carriers like FADH2 and NADH, ultimately leading to ATP synthesis.