Citric Acid Cycle: The Key to Energy Production in Eukaryotic Cells

Citric acid cycle

A chemical cycle involving eight steps that completes the metabolic breakdown of glucose molecules to carbon dioxide; occurs within the mitochondrion; the second major stage in cellular respiration.Central metabolic hum as it processes both catabolic and anabolic metabolitesAlso known as Kreb’s Cycle and tricarboxylic acid cycle (TCA)

The citric acid cycle, also known as the Krebs cycle or tricarboxylic acid cycle, is a series of chemical reactions that occur in the mitochondria of eukaryotic cells. It is a central metabolic pathway that is involved in the breakdown of carbohydrates, fats and proteins to produce adenosine triphosphate (ATP), which is the energy currency of the cell.

During the citric acid cycle, a series of enzymatic reactions convert a two-carbon molecule, acetyl-CoA, into carbon dioxide and water. The cycle involves eight steps, each of which is catalysed by a specific enzyme.

The first step of the citric acid cycle is the condensation of acetyl-CoA and oxaloacetate to form citrate, which is catalysed by the enzyme citrate synthase. Citrate is then isomerised to isocitrate by the enzyme aconitase. In the next step, isocitrate is oxidised to alpha-ketoglutarate by the enzyme isocitrate dehydrogenase, which generates NADH as a byproduct.

Alpha-ketoglutarate is then oxidised to succinyl-CoA by the enzyme alpha-ketoglutarate dehydrogenase, which also generates NADH and carbon dioxide. The next step involves the conversion of succinyl-CoA to succinate by the enzyme succinyl-CoA synthetase, which generates GTP as a byproduct.

Succinate is then oxidised to fumarate by the enzyme succinate dehydrogenase, which also generates FADH2 as a byproduct. Fumarate is then hydrated to form malate by the enzyme fumarase, and malate is oxidised to oxaloacetate by the enzyme malate dehydrogenase, which generates NADH as a byproduct.

At the end of the citric acid cycle, the starting molecule, oxaloacetate, is regenerated. The NADH and FADH2 generated during the cycle are then used by the electron transport chain to produce ATP through oxidative phosphorylation.

Overall, the citric acid cycle is a crucial pathway for energy production and is essential for the proper functioning of the cell.

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