Question

In pne Krebs cycle, decarboxylation takes place at .......... steps.

• A. Five
• B. Four
• C. Three
• D. Two

Answer 1

Answer: (D)

Two

In single Krebs cycle decarboxylation takes place at following two steps-

1. First oxidative decarboxylation takes place at fourth step where isocitrate gives off a pair of hydrogen atoms (oxidation) and a molecule of carbon-di-oxide (decarboxylation) and becomes 5-carbon α- ketoglutarate.

2. Second oxidative decarboxylation takes place at fifth step where coenzyme-A reacts with α- ketoglutarateforming 4-carbonsuccinyl-coenzyme A and releasing carbon-di-oxide and a pair of hydrogen atoms.

Thus, the correct answer is option D.