Question

The first $5C$ dicarboxylic acid in Krebs' cycle which is used in nitrogen metabolism is

• A. $OAA$
• B. citric acid
• C. $\alpha$-ketoglutaric acid
• D. acetyl coenzyme $A$

Answer 1

Answer: (C)

The first 5 carbon dicarboxylic acid in Krebs' cycle is $\alpha$ ketoglutaric acid. The $\alpha$-ketoglutarate that accumulates when $\alpha$-ketoglutarate dehydrogenase is inhibited can be used in nitrogen metabolism as a precursor for several amino acids and the purine bases.
$\alpha$-ketoglutarate $\to$ Glutamate Other amino acids $\to$ Purines.
$\alpha$-ketoglutarate of Krebs' cycle produces an important amino acid called glutamate on amination.