Question

Which reactions of the citric acid cycle reduce FAD?

Short answer

The conversion of succinate to fumarate by succinate dehydrogenase reduces FAD to FADH2.

Step-by-step solution

Identify the Citric Acid Cycle Reactions

List all the reactions that occur in the citric acid cycle. The cycle includes reactions such as citrate formation, isomerization, oxidative decarboxylations, and more.

Focus on Electron Carrier Molecules

Identify which reactions involve the reduction of electron carrier molecules such as NAD+ and FAD. Focus specifically on FAD for this task.

Locate the Specific Reaction Reducing FAD

Within the citric acid cycle, locate the reaction where FAD is reduced to FADH2.

Analyze Succinate to Fumarate Conversion

Identify the enzyme involved in the conversion of succinate to fumarate, which is succinate dehydrogenase. This reaction results in the reduction of FAD to FADH2.

Key concepts

succinate to fumarate conversion

The conversion of succinate to fumarate is a crucial reaction within the citric acid cycle. During this process, succinate undergoes an oxidation reaction. Here, succinate loses two hydrogen atoms, which are transferred to another molecule. This results in succinate being converted into fumarate.

Succinate dehydrogenase is the enzyme that catalyzes this reaction. This enzyme binds to the succinate molecule and facilitates its transformation into fumarate.

What makes this reaction particularly interesting is the role it plays in the larger cycle of reactions happening inside the mitochondria. It is one of several steps where molecules are either being built up or broken down, providing energy and important intermediates for the cell.

FAD reduction

During the conversion of succinate to fumarate, an important process known as FAD reduction occurs. FAD stands for Flavin Adenine Dinucleotide, a molecule that functions as an electron carrier.

In this specific reaction, FAD is reduced to FADH2. This means it gains two electrons and two protons from succinate, helping the succinate to convert into fumarate. The reduction of FAD to FADH2 is essential because FADH2 carries the electrons to the electron transport chain.

In the electron transport chain, these electrons will eventually be used to produce ATP, the main energy currency of the cell. This highlights how the reduction of FAD is a key step in cellular energy production.

succinate dehydrogenase

Succinate dehydrogenase is the enzyme that plays a vital role in the conversion of succinate to fumarate within the citric acid cycle. It's unique because it is the only enzyme that is part of both the citric acid cycle and the electron transport chain.

This protein complex is located in the inner mitochondrial membrane. It binds to the succinate molecule and catalyzes its conversion to fumarate while reducing FAD to FADH2.

One key feature of succinate dehydrogenase is that it is embedded within the mitochondrial membrane. This positioning allows it to directly transfer the electrons obtained from FADH2 into the electron transport chain, making the energy conversion process more efficient.

• Located in the inner mitochondrial membrane
• Part of both the citric acid cycle and the electron transport chain
• Directly transfers electrons from FADH2 to the electron transport chain

This makes succinate dehydrogenase a crucial component in energy production within cells.