Which of the following molecules will produce the most ATP per mole? (18.5, 18.6)


e. α-ketoglutarate or fumarate in one turn of the citric acid cycle

Verified step by step guidance

1. Identify the role of each molecule in the citric acid cycle: $\alpha$-ketoglutarate and fumarate.
2. Understand that $\alpha$-ketoglutarate is converted to succinyl-CoA, producing NADH, which can generate ATP through oxidative phosphorylation.
3. Recognize that fumarate is converted to malate, which is then converted to oxaloacetate, producing FADH2 and NADH, both of which contribute to ATP production.
4. Compare the ATP yield from NADH and FADH2: NADH typically produces more ATP than FADH2.
5. Determine which molecule, $\alpha$-ketoglutarate or fumarate, results in more NADH production, and thus more ATP, in one turn of the citric acid cycle.

Key Concepts

Citric Acid Cycle

The citric acid cycle, also known as the Krebs cycle, is a key metabolic pathway that occurs in the mitochondria. It involves a series of chemical reactions that convert acetyl-CoA into carbon dioxide and high-energy electron carriers, such as NADH and FADH2. These carriers are crucial for ATP production in the electron transport chain, making the cycle essential for cellular respiration.

ATP Yield from Metabolites

Different metabolites yield varying amounts of ATP when processed through the citric acid cycle and subsequent oxidative phosphorylation. For instance, α-ketoglutarate and fumarate are intermediates in the cycle, but their conversion into ATP differs based on the number of high-energy electron carriers produced. Understanding the ATP yield from each metabolite is vital for determining which produces the most energy.

Oxidative Phosphorylation

Oxidative phosphorylation is the final stage of cellular respiration, where the energy from NADH and FADH2 is used to generate ATP. This process occurs in the inner mitochondrial membrane and involves the electron transport chain and ATP synthase. The efficiency of ATP production during this stage is influenced by the number of electrons transferred from the metabolites, making it essential to consider when evaluating ATP yield.