which is correct???

Solution:

Ans. Option 3) is correct: Pyruvic acid to Acetyl CoA

 

Krebs cycle or TCA cycle is a set of biochemical reactions which are a part of aerobic respiration and utilize acetate generated from carbohydrates, fats and proteins for generation of energy. It also generates NADH in the process.

Krebs cycle takes place in the mitochondrial matrix and involves complete oxidation of pyruvate generated through glycolysis  by stepwise removal of all hydrogen atoms, which leaves three molecules of CO2.

Steps:

  • Acetyl group condenses with oxaloacetic acid and water to yield citric acid (catalysed by the enzyme citrate synthase)
  • Citrate isomerises into isocitrate
  • Two successive decarboxylation steps follow, leading to the formation of α ketoglutaric acid, followed by succinyl CoA
  • This is followed by the conversion of succinyl CoA into succinic acid (substrate level phosphorylation). In a coupled reaction, GTP is converted into GDP, simultaneously synthesising ATP from ADP.
  • Conversion of one molecule of pyruvate into acetyl CoA yields 1 molecule of CO2 and 1NADH.
  • One Krebs cycle yields 2CO2 + 3NADH + 1FADH 2 + 1ATP
 
 

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