How many NADH and how many FADH₂ molecules are formed in the citric acid cycle?

Verified step by step guidance

1. Understand the citric acid cycle: The citric acid cycle (also known as the Krebs cycle or TCA cycle) is a series of chemical reactions used by aerobic organisms to generate energy through the oxidation of acetyl-CoA. It also produces electron carriers like NADH and FADH2, which are used in the electron transport chain to produce ATP.
2. Identify the key steps in the citric acid cycle where NADH is produced: NADH is formed during three specific reactions in the cycle. These occur during the oxidation of isocitrate to α-ketoglutarate, the oxidation of α-ketoglutarate to succinyl-CoA, and the oxidation of malate to oxaloacetate.
3. Identify the step in the citric acid cycle where FADH2 is produced: FADH2 is formed during the oxidation of succinate to fumarate, which is catalyzed by the enzyme succinate dehydrogenase.
4. Count the number of NADH molecules produced per turn of the cycle: Since there are three reactions that produce NADH, one turn of the citric acid cycle generates three NADH molecules.
5. Count the number of FADH2 molecules produced per turn of the cycle: Since there is one reaction that produces FADH2, one turn of the citric acid cycle generates one FADH2 molecule.

Key Concepts

Citric Acid Cycle

The citric acid cycle, also known as the Krebs cycle, is a series of chemical reactions used by all aerobic organisms to generate energy. It occurs in the mitochondria and is a key component of cellular respiration, where acetyl-CoA is oxidized to produce energy carriers, including NADH and FADH2.

NADH and FADH2

NADH and FADH2 are electron carriers produced during the citric acid cycle. NADH is generated from the reduction of NAD+ during specific reactions, while FADH2 is produced from the reduction of FAD. Both molecules play a crucial role in the electron transport chain, where they help generate ATP.

Energy Yield

The energy yield from the citric acid cycle is significant, as it produces three NADH and one FADH2 per turn of the cycle. Since each NADH can generate approximately 2.5 ATP and each FADH2 about 1.5 ATP during oxidative phosphorylation, understanding their production is essential for calculating the total energy output from glucose metabolism.