Succinate dehydrogenase

Definition

Succinate dehydrogenase is an enzyme that plays a crucial role in both the citric acid cycle and the electron transport chain. It catalyzes the conversion of succinate to fumarate while reducing flavin adenine dinucleotide (FAD) to FADH2. This enzyme links the citric acid cycle with oxidative phosphorylation, as the FADH2 produced is subsequently utilized in the electron transport chain to generate ATP through chemiosmosis.

5 Must Know Facts For Your Next Test

1. Succinate dehydrogenase is unique because it is the only enzyme that participates in both the citric acid cycle and the electron transport chain.
2. It is found in the inner mitochondrial membrane and is part of complex II of the electron transport chain.
3. The reaction catalyzed by succinate dehydrogenase is considered an irreversible step in the citric acid cycle.
4. Dysfunction of succinate dehydrogenase can lead to a variety of metabolic disorders and has been linked to certain cancers.
5. The FADH2 produced by succinate dehydrogenase generates fewer ATP molecules compared to NADH produced by other dehydrogenases, as it enters the electron transport chain at a lower energy level.

Review Questions

• How does succinate dehydrogenase connect the citric acid cycle to oxidative phosphorylation?
  • Succinate dehydrogenase connects the citric acid cycle to oxidative phosphorylation by catalyzing the conversion of succinate to fumarate while producing FADH2. This FADH2 then enters the electron transport chain, contributing to ATP production through chemiosmosis. Essentially, succinate dehydrogenase serves as a link between these two vital metabolic pathways, enabling energy production from both carbohydrate and fat metabolism.
• What role does succinate dehydrogenase play in cellular respiration, particularly regarding energy production?
  • In cellular respiration, succinate dehydrogenase is critical for energy production because it oxidizes succinate into fumarate while reducing FAD to FADH2. This process not only helps complete the citric acid cycle but also provides electrons that are shuttled into the electron transport chain. The subsequent oxidation of FADH2 leads to the formation of a proton gradient across the inner mitochondrial membrane, ultimately driving ATP synthesis via ATP synthase.
• Evaluate the implications of succinate dehydrogenase malfunction on human health, considering metabolic disorders and cancer.
  • Malfunction or mutations in succinate dehydrogenase can lead to significant health issues, including various metabolic disorders such as fumaric aciduria. Additionally, impaired function of this enzyme has been linked to certain types of cancer, particularly familial paraganglioma and pheochromocytoma. The connection lies in altered metabolic signaling and energy production pathways, leading to increased reactive oxygen species and other metabolites that can drive tumorigenesis. Understanding these links provides insight into potential therapeutic targets for diseases associated with succinate dehydrogenase dysfunction.

Related terms

FADH2: A reduced form of flavin adenine dinucleotide that serves as an electron carrier in the electron transport chain.

Citric Acid Cycle: A series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetate derived from carbohydrates, fats, and proteins.

Electron Transport Chain: A sequence of protein complexes and other molecules that transfer electrons through redox reactions to create a proton gradient that drives ATP synthesis.