FADH2

Definition

FADH2 is a reduced coenzyme that plays a crucial role in various metabolic pathways, including the biosynthesis of steroids, the catabolism of triacylglycerols, and the citric acid cycle. It is the reduced form of flavin adenine dinucleotide (FAD), a cofactor essential for many oxidation-reduction reactions in the body.

5 Must Know Facts For Your Next Test

1. FADH2 is a key cofactor in the β-oxidation of fatty acids, providing electrons to the electron transport chain and contributing to the generation of ATP.
2. In the citric acid cycle, FADH2 is produced during the oxidation of succinate to fumarate, which is then reoxidized to FAD in the electron transport chain.
3. FADH2 is also involved in the biosynthesis of steroids, where it provides reducing power for the conversion of lanosterol to cholesterol.
4. The conversion of FAD to FADH2 and vice versa is an essential redox reaction in many metabolic pathways, allowing for the efficient transfer of electrons and the production of ATP.
5. The ability of FADH2 to participate in oxidation-reduction reactions makes it a crucial component in the regulation of cellular energy production and metabolism.

Review Questions

• Explain the role of FADH2 in the catabolism of triacylglycerols through β-oxidation.
  • FADH2 plays a critical role in the β-oxidation of fatty acids, which is the process of breaking down triacylglycerols to generate acetyl-CoA for entry into the citric acid cycle. During β-oxidation, FADH2 is produced when the enzyme acyl-CoA dehydrogenase catalyzes the dehydrogenation of acyl-CoA intermediates. The FADH2 then transfers its electrons to the electron transport chain, contributing to the generation of ATP through oxidative phosphorylation. This process allows the body to efficiently convert the energy stored in triacylglycerols into a usable form, ATP, which can be utilized by cells for various metabolic activities.
• Describe the involvement of FADH2 in the citric acid cycle and its connection to energy production.
  • In the citric acid cycle, FADH2 is produced during the oxidation of succinate to fumarate, catalyzed by the enzyme succinate dehydrogenase. The FADH2 then enters the electron transport chain, where it donates its electrons to the respiratory complexes. This electron transfer process ultimately drives the production of ATP through the process of oxidative phosphorylation. The FADH2 generated in the citric acid cycle is therefore a critical intermediate in the larger metabolic pathway that converts the energy stored in organic molecules, such as glucose and fatty acids, into the universal energy currency, ATP, which can be used by cells to power a wide range of metabolic processes.
• Analyze the role of FADH2 in the biosynthesis of steroids and explain how this process is linked to overall metabolic regulation.
  • FADH2 is involved in the biosynthesis of steroids, such as cholesterol, by providing reducing power for the conversion of lanosterol to cholesterol. Specifically, FADH2 acts as a cofactor for enzymes that catalyze the removal of methyl groups and the introduction of double bonds in the steroid precursor molecules. This step in the steroid biosynthesis pathway is important because cholesterol is a precursor for the synthesis of other steroid hormones, such as testosterone, estrogen, and cortisol. These hormones play crucial roles in regulating a wide range of physiological processes, including growth, development, metabolism, and the stress response. By participating in the biosynthesis of these important regulatory molecules, FADH2 is indirectly involved in the overall metabolic control and homeostasis of the body. The ability of FADH2 to facilitate these metabolic transformations highlights its central role in integrating various biochemical pathways and maintaining the delicate balance of the body's metabolism.

Related terms

Flavin Adenine Dinucleotide (FAD): FAD is a cofactor that acts as an electron acceptor in many enzymatic reactions, particularly in the citric acid cycle and the electron transport chain.

Oxidation-Reduction Reactions: Redox reactions involve the transfer of electrons between molecules, where one molecule is oxidized (loses electrons) and another is reduced (gains electrons).

Electron Transport Chain: The electron transport chain is a series of protein complexes that facilitate the transfer of electrons, ultimately leading to the production of ATP through the process of oxidative phosphorylation.