Tricarboxylic acid

Tricarboxylic acids are organic compounds that contain three carboxyl functional groups (-COOH). These acids are important in various biochemical processes, most notably in the citric acid cycle, also known as the tricarboxylic acid cycle or Krebs cycle, which is a key metabolic pathway that unifies carbohydrate, fat, and protein metabolism.

Isocitric acid structure

Structure and Properties

Tricarboxylic acids are characterized by the presence of three carboxyl groups. These groups can donate protons, making the compounds acidic. The general formula for a tricarboxylic acid is C₆H₈O₇, although variations exist depending on the specific structure of the acid.

Citric Acid

Citric acid is one of the most well-known tricarboxylic acids. It is a weak organic acid that is a natural preservative and is also used to add an acidic or sour taste to foods and drinks. Citric acid is a key intermediate in the citric acid cycle, which occurs in the metabolism of all aerobic organisms.

Cis-Aconitic Acid

Cis-aconitic acid structure

Cis-aconitic acid is formed from citric acid by the removal of a molecule of water. It is then converted to isocitric acid by the addition of water.

Trans-Aconitic Acid

Trans-aconitic acid structure

Isocitric Acid

Isocitric acid is an isomer of citric acid. It is also an intermediate in the citric acid cycle. The conversion of citric acid to isocitric acid is catalyzed by the enzyme aconitase.

Aconitic Acid

Aconitic acid exists in two isomeric forms: cis-aconitic acid and trans-aconitic acid. These acids are intermediates in the conversion of citric acid to isocitric acid in the citric acid cycle.

Trans-aconitic acid is a less common isomer of aconitic acid. It is not typically involved in the citric acid cycle but can be found in some plant species.

Biological Importance

Tricarboxylic acids play a crucial role in the citric acid cycle, which is essential for the production of energy in aerobic organisms. This cycle is a series of chemical reactions used by all aerobic organisms to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins.

Related Pages

• Citric acid cycle
• Carboxylic acid
• Metabolism
• Aconitase

Acetyl-CoA + H2O	Oxaloacetate NADH +H+ NAD+ Malate   H2O Fumarate FADH2 FAD Succinate CoA + ATP (GTP) Pi + ADP (GDP) Succinyl-CoA
			NADH + H+ + CO2
CoA			NAD+
	Citrate   H2O cis-Aconitate H2O   Isocitrate NAD(P)+ NAD(P)H +  H+ Oxalosuccinate   CO2 2-oxoglutarate