Question

During photorespiration the number of glycine molecules giving rise to one molecule of $C{O}_2$ are

• A. 2
• B. 1
• C. 4
• D. 3

Answer 1

The correct option is A 2

Photorespiration (also known as the oxidative photosynthetic carbon cycle, or C2 photosynthesis) is a process in plant metabolism which attempts to reduce the consequences of a wasteful oxygenation reaction by the enzyme RuBisCO. The desired reaction is the addition of carbon dioxide to RuBP (carboxylation), a key step in the Calvin Benson cycle, however approximately 25% of reactions by RuBisCO instead add oxygen to RuBP (oxygenation), producing a product that cannot be used within the CalvinBenson cycle. The conversion of 2x 2 carbon glycine to 1 C3 serine in the mitochondria by the enzyme glycine-decarboxylase is a key step, which releases CO${}_2$, NH${}_3$3, and reduces NAD to NADH.Thus, during photo respiration the number of glycine molecules giving rise to one molecule of CO${}_2$ are 2. So, option A is correct and other options are incorrect.