explain the citric acid cycle/kerb's cycle/tricarboxylic acid cycle..
Answers
Answer:
The citric acid cycle – also known as the TCA or the Krebs 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, into adenosine triphosphate and carbon dioxide.
The cycle was first elucidated by scientist “Sir Hans Adolf Krebs” (1900 to 1981). He shared the Nobel Prize for physiology and Medicine in 1953 with Fritz Albert Lipmann, the father of ATP cycle.
The process oxidises glucose derivatives, fatty acids and amino acids to carbon dioxide (CO2) through a series of enzyme controlled steps. The purpose of the Krebs Cycle is to collect (eight) high-energy electrons from these fuels by oxidising them, which are transported by activated carriers NADH and FADH2 to the electron transport chain. The Krebs Cycle is also the source for the precursors of many other molecules, and is therefore an amphibolic pathway (meaning it is both anabolic and catabolic).
Krebs (Citric Acid) Cycle Steps by Steps Explanation
The Net Equation
acetyl CoA + 3 NAD + FAD + ADP + HPO4-2 —————> 2 CO2 + CoA + 3 NADH+ + FADH+ + ATP
Reaction 1: Formation of Citrate
The first reaction of the cycle is the condensation of acetyl-CoA with oxaloacetate to form citrate, catalyzed by citrate synthase. Once oxaloacetate is joined with acetyl-CoA, a water molecule attacks the acetyl leading to the release of coenzyme A from the complex.
Reaction 2: Formation of Isocitrate
The citrate is rearranged to form an isomeric form, isocitrate by an enzyme acontinase. In this reaction, a water molecule is removed from the citric acid and then put back on in another location. The overall effect of this conversion is that the –OH group is moved from the 3′ to the 4′ position on the molecule. This transformation yields the molecule isocitrate.
Reaction 3: Oxidation of Isocitrate to α-Ketoglutarate
In this step, isocitrate dehydrogenase catalyzes oxidative decarboxylation of isocitrate to form α-ketoglutarate. In the reaction, generation of NADH from NAD is seen. The enzyme isocitrate dehydrogenase catalyzes the oxidation of the –OH group at the 4′ position of isocitrate to yield an intermediate which then has a carbon dioxide molecule removed from it to yield alpha-ketoglutarate.
Reaction 4: Oxidation of α-Ketoglutarate to Succinyl-CoA
Alpha-ketoglutarate is oxidized, carbon dioxide is removed, and coenzyme A is added to form the 4-carbon compound succinyl-CoA. During this oxidation, NAD+ is reduced to NADH + H+. The enzyme that catalyzes this reaction is alpha-ketoglutarate dehydrogenase.
Reaction 5: Conversion of Succinyl-CoA to Succinate
CoA is removed from succinyl-CoA to produce succinate. The energy released is used to make guanosine triphosphate (GTP) from guanosine diphosphate (GDP) and Pi by substrate-level phosphorylation. GTP can then be used to make ATP. The enzyme succinyl-CoA synthase catalyzes this reaction of the citric acid cycle.
Reaction 6: Oxidation of Succinate to Fumarate
Succinate is oxidized to fumarate. During this oxidation, FAD is reduced to FADH2. The enzyme succinate dehydrogenase catalyzes the removal of two hydrogens from succinate.
Reaction 7: Hydration of Fumarate to Malate
The reversible hydration of fumarate to L-malate is catalyzed by fumarase (fumarate hydratase). Fumarase continues the rearrangement process by adding Hydrogen and Oxygen back into the substrate that had been previously removed.
Reaction 8: Oxidation of Malate to Oxaloacetate
Malate is oxidized to produce oxaloacetate, the starting compound of the citric acid cycle by malate dehydrogenase. During this oxidation, NAD+ is reduced to NADH + H+.
Explanation:
this is the whole explanation of the citric acid cycle with steps......hope it helps.......plz mark my answer as brainliest and also follow me