key term - Succinate dehydrogenase

Definition

Succinate dehydrogenase is an enzyme that plays a critical role in the citric acid cycle by catalyzing the oxidation of succinate to fumarate while reducing ubiquinone to ubiquinol. This enzyme is unique as it is the only one that participates in both the citric acid cycle and the electron transport chain, linking these two essential metabolic pathways. Its function is crucial for energy production in aerobic respiration.

5 Must Know Facts For Your Next Test

1. Succinate dehydrogenase is a flavoprotein, containing a covalently bound FAD molecule that is essential for its catalytic activity.
2. This enzyme is located in the inner mitochondrial membrane, making it strategically positioned to funnel electrons directly into the electron transport chain.
3. The reaction catalyzed by succinate dehydrogenase is reversible, though it primarily functions in the oxidative direction during aerobic respiration.
4. Dysfunction of succinate dehydrogenase has been linked to various metabolic disorders and some forms of cancer, highlighting its importance in cellular metabolism.
5. Succinate dehydrogenase helps maintain the balance of redox states within the mitochondria by facilitating the transfer of electrons from succinate to ubiquinone.

Review Questions

• How does succinate dehydrogenase connect the citric acid cycle with oxidative phosphorylation?
  • Succinate dehydrogenase serves as a crucial link between the citric acid cycle and oxidative phosphorylation by catalyzing the conversion of succinate to fumarate while reducing ubiquinone to ubiquinol. This reaction not only facilitates energy extraction during the citric acid cycle but also feeds electrons into the electron transport chain, allowing for ATP production. This dual role underscores its importance in both metabolic pathways.
• Discuss the role of FAD and how it contributes to the function of succinate dehydrogenase in cellular respiration.
  • FAD acts as a prosthetic group for succinate dehydrogenase, playing a vital role in its enzymatic function. During the oxidation of succinate to fumarate, FAD is reduced to FADH2, which then participates in the electron transport chain by donating electrons to ubiquinone. This process contributes to ATP generation and helps maintain efficient energy metabolism within the cell.
• Evaluate the implications of succinate dehydrogenase dysfunction on cellular metabolism and health.
  • Dysfunction of succinate dehydrogenase can have serious implications for cellular metabolism and health, as it disrupts both the citric acid cycle and oxidative phosphorylation. This can lead to an accumulation of succinate and a decrease in ATP production, potentially causing metabolic disorders and contributing to various diseases, including certain cancers. Understanding these dysfunctions provides insight into how critical this enzyme is for maintaining metabolic balance and overall cellular health.

Related terms

Citric Acid Cycle: A series of enzymatic reactions that takes place in the mitochondria, converting acetyl-CoA into carbon dioxide and capturing energy through ATP and electron carriers.

Ubiquinone:

Also known as coenzyme Q, it is a lipid-soluble molecule that acts as an electron carrier in the electron transport chain, accepting electrons from succinate dehydrogenase.

FADH2:

A reduced form of flavin adenine dinucleotide that carries electrons to the electron transport chain, generated during the conversion of succinate to fumarate by succinate dehydrogenase.