FADH2

Definition

FADH2 is a coenzyme that plays a critical role in cellular respiration as a carrier of electrons and protons during metabolic reactions. It is produced during the Krebs cycle and is essential for generating energy in the form of ATP through oxidative phosphorylation, linking several important biochemical processes.

5 Must Know Facts For Your Next Test

1. FADH2 is generated during the Krebs cycle when succinate is converted to fumarate by the enzyme succinate dehydrogenase.
2. Each molecule of FADH2 can produce approximately 1.5 molecules of ATP when it donates electrons to the electron transport chain.
3. FADH2 donates its electrons at a lower energy level in the electron transport chain compared to NADH, leading to less ATP production.
4. FADH2 is involved in fatty acid oxidation, where it helps convert fatty acids into acetyl-CoA for energy production.
5. In addition to energy production, FADH2 also participates in various redox reactions throughout metabolism, serving as an important electron donor.

Review Questions

• How does FADH2 contribute to ATP production during oxidative phosphorylation?
  • FADH2 contributes to ATP production by donating electrons to the electron transport chain, specifically at Complex II. As electrons move through the chain, they facilitate the pumping of protons across the mitochondrial membrane, creating a proton gradient. This gradient drives ATP synthesis through ATP synthase when protons flow back into the mitochondrial matrix, ultimately resulting in ATP production from the energy released by the electron transfer.
• Compare and contrast the roles of FADH2 and NADH in cellular respiration and their impact on ATP yield.
  • Both FADH2 and NADH are crucial for cellular respiration as they act as electron carriers. However, NADH donates its electrons at Complex I of the electron transport chain, allowing for a higher energy yield (approximately 2.5 ATP per NADH) than FADH2, which donates electrons at Complex II and yields about 1.5 ATP per molecule. This difference in their entry point into the chain influences the total amount of ATP produced from glucose metabolism.
• Evaluate the significance of FADH2 in lipid metabolism and how it integrates with overall energy production in cells.
  • FADH2 plays a vital role in lipid metabolism, particularly during beta-oxidation of fatty acids. In this process, fatty acids are broken down into acetyl-CoA units, generating FADH2 and NADH along the way. The presence of FADH2 not only provides a direct source of reducing power for energy production through oxidative phosphorylation but also highlights how lipid catabolism is integrated into cellular energy homeostasis. The ability to convert stored fats into usable energy via pathways involving FADH2 underscores its importance in maintaining metabolic flexibility in response to varying energy demands.

Related terms

NADH: NADH is another coenzyme that carries electrons and protons, similar to FADH2, but it is produced in different metabolic pathways, including glycolysis and the Krebs cycle.

Krebs Cycle: The Krebs cycle, also known as the citric acid cycle, is a series of enzymatic reactions that generates FADH2 and NADH by oxidizing acetyl-CoA to produce ATP, CO2, and high-energy electron carriers.

Oxidative Phosphorylation: Oxidative phosphorylation is the final stage of cellular respiration, where the electrons from FADH2 and NADH are transferred through the electron transport chain to ultimately produce ATP.