Question

Which of the following enzymes helps in fixing $CO_{2}$ into malic acid in sorghum plant?

• A. RuBP carboxylase
• B. PEP carboxylase
• C. Pentose phosphatase
• D. Fructose phosphatase

Hint:

$C_4$ plants use PEP carboxylase because it has a high affinity for $CO_2$ and no affinity for $O_2$.

Answer 1

The Correct Option is B

Step 1: Concept
Sorghum is a $C_4$ plant that uses a specific pathway to minimize photorespiration.
Step 2: Analysis
In $C_4$ plants, the initial $CO_2$ fixation occurs in the mesophyll cells. The enzyme PEP carboxylase (Phosphoenolpyruvate carboxylase) catalyzes the fixation of $CO_2$ into a 4-carbon acid (oxaloacetic acid), which is then converted to malic acid.
Step 3: Conclusion
Hence, PEP carboxylase is the enzyme responsible.
Final Answer:(B)