In C4 pathway the fixation of CO2 by PEPCase occurs ina)Palisade tissueb)Mesophyllc)Bundle sheathd)Gaurd cellCorrect answer is option 'B'. Can you explain this answer?

Question

Answer

In the C4 pathway, initial carbon fixation takes place in mesophyll cells and the Calvin cycle takes place in bundle-sheath cells. PEP carboxylase attaches an incoming carbon dioxide molecul to the three-carbon molecule PEP, producing oxaloacetate (a four-carbon molecule).

Answer

Answer

Introduction to C4 Pathway
The C4 pathway is a crucial photosynthetic process that enhances CO2 fixation, especially in hot and arid environments. Understanding where this fixation occurs is essential for grasping plant physiology.

PEPCase Function
- Phosphoenolpyruvate Carboxylase (PEPCase) is the enzyme responsible for the initial fixation of CO2 in the C4 pathway.
- It catalyzes the reaction between CO2 and phosphoenolpyruvate (PEP) to form oxaloacetate, a four-carbon compound.

Location of CO2 Fixation
- CO2 fixation by PEPCase occurs primarily in the **mesophyll cells** of the leaves.
- The mesophyll cells are strategically located to capture atmospheric CO2, making them the first point of contact in the C4 photosynthetic pathway.

Role of Mesophyll Cells
- Mesophyll cells contain high concentrations of PEPCase, facilitating efficient CO2 uptake.
- After CO2 fixation, the oxaloacetate produced is converted into malate or aspartate, which is then transported to bundle sheath cells.

Bundle Sheath and Final Steps
- While the final steps of the C4 pathway occur in **bundle sheath cells**, where the Calvin cycle takes place, CO2 fixation itself is initiated in the mesophyll.
- This spatial separation is key to minimizing photorespiration and optimizing photosynthetic efficiency.

Conclusion
In summary, the fixation of CO2 by PEPCase in the C4 pathway occurs in the **mesophyll cells**, making option 'B' the correct answer. This adaptation allows plants to thrive in conditions that would otherwise limit photosynthesis.

Similar NEET Doubts

Which of the following statements regarding the C4pathway is false?

Carbon refixation in C4 plants occurs in chloroplasts of :–

In C4 plants, initial CO2 fixation takes place in the chloroplasts of : [C.G. PMT 2004]

In which of the following pathways, movement of water occurs from one cell to another cell through plasmodesmata?

How do C4 and CAM plants utilize different carbon fixation pathways?

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