Question

During dark reaction 2 PGA are derived from

• A. CO${}_2$ and RUBP
• B. CO${}_2$
• C. RUBP
• D. CO${}_2$, PEP and RUBP

Answer 1

Answer: (A)

CO${}_2$ and RUBP

Photorespiration includes oxidation of RuBP, rather than carboxylation, by enzyme RUBISCO and forms 2-phosphoglycolate (2 PGA). Dephosphorylation of 2 phosphoglycolate forms glycolate which in turn enters peroxisomes and is then transaminated to glycine. PEP is the primary acceptor of CO${}_2$ in C${}_4$ plants while RuBP is the primary acceptor in C${}_3$ plants. PEP is the primary acceptor of CO${}_2$ in C${}_4$ plants.

So, the correct answer is option A.