Which reactions of the citric acid cycle transfer energy as NADH?

Verified step by step guidance

1. Identify the reactions in the citric acid cycle where NAD⁺ is reduced to NADH. This occurs during specific oxidation steps where electrons are transferred to NAD⁺.
2. The first reaction is the conversion of isocitrate to α-ketoglutarate. This is catalyzed by the enzyme isocitrate dehydrogenase, and NAD⁺ is reduced to NADH in the process.
3. The second reaction is the conversion of α-ketoglutarate to succinyl-CoA. This is catalyzed by the enzyme α-ketoglutarate dehydrogenase, and again, NAD⁺ is reduced to NADH.
4. The third reaction is the conversion of malate to oxaloacetate. This is catalyzed by the enzyme malate dehydrogenase, and NAD⁺ is reduced to NADH during this step.
5. Summarize that these three reactions—(1) isocitrate to α-ketoglutarate, (2) α-ketoglutarate to succinyl-CoA, and (3) malate to oxaloacetate—are the steps in the citric acid cycle where energy is transferred as NADH.

Key Concepts

Citric Acid Cycle

The citric acid cycle, also known as the Krebs cycle, is a series of enzymatic reactions that occur in the mitochondria. It plays a crucial role in cellular respiration by oxidizing acetyl-CoA to produce energy carriers. The cycle generates NADH and FADH2, which are essential for the electron transport chain, ultimately leading to ATP production.

NADH Production

NADH is a reduced form of nicotinamide adenine dinucleotide (NAD+), a key electron carrier in metabolic processes. In the citric acid cycle, specific reactions, such as the conversion of isocitrate to alpha-ketoglutarate and malate to oxaloacetate, involve the reduction of NAD+ to NADH. This process captures energy that can later be used to generate ATP.

Energy Transfer in Metabolism

Energy transfer in metabolism refers to the conversion of biochemical energy from nutrients into usable forms, primarily ATP. In the citric acid cycle, the transfer of electrons to NAD+ during specific reactions is a critical step in this process. The resulting NADH carries high-energy electrons to the electron transport chain, where they are used to produce ATP through oxidative phosphorylation.