The tricarboxylic acid (TCA) cycle is a series of reactions that generate energy in the form of ATP and reduced coenzyme molecules. (NADH2 and FADH2). This cycle also performs other functions. Many intermediates in this cycle are precursors in the biosynthesis of amino acids, purines, pyrimidines, and so on. Thus, the TCA cycle is an amphibian cycle, meaning that it functions not only in catabolic reactions (decomposition) but also in anabolic reactions (synthesis).
The citric acid cycle
The citric acid cycle is also often referred to as the Kreb’s cycle or the tricarboxylic acid cycle and takes place inside the mitochondria. The citric acid cycle is the final pathway with the oxidation of carbohydrates, lipids, and proteins. The citric acid cycle is a series of acetyl CoA catabolism reactions that produce energy in the form of ATP.
During the oxidation process of Koa acetyl, a reducing agent is formed in the form of hydrogen or electrons. This reducing element equivalent then enters the respiration chain (oxidative phosphorylation process) to produce ATP. In conditions without oxygen (anoxide) or lack of oxygen (hypoxide) there is a total resistance in the cycle.
The stages of Kreb’s cycle (TCA cycle)
In this cycle pyruvic acid is produced in glycolysis. The first time pyruvic acid loses one carbon atom through CO2, and the remaining molecules will join coenzyme A. The result of this reaction is acetyl CoA (door reaction)
In the acetyl reaction the CoA joins with the oxaloacetic acid (4 carbon acids) to form:
- The formation of citric acid (6 carbon acid), the formation of citrate carried out by citric synthesis also known as the enzyme that causes condensation of citrate or oxalo acetate liase
2. The formation of isocitrate (6 carbon), the enzyme akonitase catalyzes the reversible hydration of tricarboxylic acid anions that produce isocitrates.
3. Alfaketoglutarat acid (5 carbon acid) and release one CO2 molecule - Succinic acid (4 carbon) when alfaketoglurat acid is converted to succinic acid. One more carbon atom released in the form of CO2
5. Fumaric acid (4 carbon)
6. Moleic acid (4 carbon)
7. Oxaloacetic acid, is the last step of the Kreb’s cycle and a complete cycle is formed.
Kreb’s cycle is a common pathway for carbohydrate oxidation to form CO2 and H2O.TCA CYCLE
The TCA cycle shows enzymes, substrates and products. The GTP generated during the succinate thiokinase (succinyl-CoA synthetase) reaction is equivalent to a mole of ATP by virtue of the presence of nucleoside diphosphokinase. The GTP produced during succinate thiokinase (succinyl-CoA synthetase) reaction is equivalent to one mole of ATP based on the presence of diphosphokinase nucleosides. 3 moles of NADH and 1 mole of FADH 2 produced during each cycle of the cycle are inserted into the oxidative phosphorylation pathway. Every mole of NADH produces 3 moles of ATP and every mole of FADH 2 produces 2 moles of ATP. Therefore, for every mole of pyruvate that enters the TCA cycle, 12 moles of ATP can be produced. IDH = isocitrate dehydrogenase. IDH = Isositrate dehydrogenase. α-KGDH = α-ketoglutarate dehydrogenase. KGDH = α-α-ketoglutarate dehydrogenase. MDH = malate dehydrogenase.
In the TCA cycle there are compounds that are useful as precursors in biosynthesis of as.amino, purines, primidines, etc.
