Arrange the following steps involved in the Hatch and Slack cycle in correct sequence: (A) Carboxylation of Phosphoenol Pyruvate (B) Splitting of Malate (C) Breakdown of Oxaloacetate (D) Phosphorylation of Pyruvate
Choose the correct answer from the options given below:

Correct option is A

The correct answer is (A) (A), (C), (B), (D)

Explanation:
• The Hatch and Slack cycle (C4 cycle) occurs in plants like maize and sugarcane to minimize photorespiration.
• Step 1: Carboxylation of Phosphoenol Pyruvate (PEP) (A) in the mesophyll cells to form Oxaloacetate (OAA).
• Step 2: Breakdown/Conversion of Oxaloacetate (C) into Malate or Aspartate.
• Step 3: Transport of Malate to bundle sheath cells followed by the Splitting of Malate (B) to release CO2 (which enters the Calvin cycle) and Pyruvate.
• Step 4: Transport of Pyruvate back to mesophyll cells followed by the Phosphorylation of Pyruvate (D) to regenerate PEP, completing the cycle.

Information Booster:
• The primary enzyme for carboxylation in C4 plants is PEP carboxylase (PEPcase), which has a higher affinity for CO2 than RuBisCO.
• C4 plants exhibit Kranz anatomy, characterized by the presence of bundle sheath cells.

Additional Knowledge:
• (Option B, C, D): These options misplace the sequence of regeneration or initial fixation. For instance, Pyruvate phosphorylation (D) must happen last to restart the cycle, and splitting of malate (B) cannot happen before the 4-carbon acid is formed.