How many oxidation and decarboxylation takes place in Kreb's cycle ?

 TCA undergoes 4 oxidations and 2 decarboxylations.

The correct answer is Option (3)-  TCA undergoes 4 oxidations and 2 decarboxylations.

Tricarboxylic Acid Cycle

The TCA cycle starts with the condensation of acetyl group with oxaloacetic acid (OAA) and water to yield citric acid . The reaction is catalysed by the enzyme citrate synthase and a molecule of CoA is released. Citrate is then isomerised to isocitrate. It is followed by two successive steps of decarboxylation, leading to the formation of α-ketoglutaric acid and then succinyl-CoA.

In Kreb's cycle the oxidation or dehydrogenation reaction occurs 4 times as follows:

Isocitrate to alpha-ketoglutarate (NADH is formed)

alpha-ketoglutarate to succinyl co-A (NADH is formed)

Succinate to Fumarate (FADH2​ is formed).

Malate to oxaloacetate (NADH is formed).