Question

Select the incorrect pair.

• A. 2-carbon compound - PEP
• B. 3-carbon compound - PGA
• C. 4-carbon compound - Malic acid
• D. 5-carbon compound - RuBP

Answer 1

The correct option is A 2-carbon compound - PEP

PEP (phosphoenol pyruvate) carboxylation gives the four-carbon organic acid oxaloacetate (OAA), which is rapidly converted into the organic acids malate or aspartate. These acids are then transported to the inner compartment where a decarboxylating enzyme breaks them down to $C{O}_2$ and either pyruvate (in most species) or PEP. Hence, PEP is a three carbon compound. Hence, option a is incorrectly matched.

Phosphoglyceric acid, malic acid and ribulose 1,5-bisphosphate are three, four and five carbon compounds respectively.