During Hatch - Slack pathway of `CO_2` reduction , `C_4` - acids are broken down to release `CO_2` and a - 3 carbon molecule in

Options

A. Mesophyll chloroplast
B. Bundle sheath chloroplast
C. Bundle sheath cytosol
D. Mesophyll cytosol

Answer

To solve the question regarding the Hatch-Slack pathway of CO2 reduction, we will break down the process step by step.

### Step-by-Step Solution:

1. **Understanding the Hatch-Slack Pathway**: The Hatch-Slack pathway is a type of C4 photosynthesis that occurs in certain plants. It involves the fixation of CO2 into a 4-carbon compound.

2. **Initial CO2 Fixation**: The initial fixation of CO2 occurs in the mesophyll cells of the plant. Here, CO2 is combined with phosphoenolpyruvate (PEP), a 3-carbon molecule, to form a 4-carbon compound (oxaloacetic acid or OAA).

3. **Formation of C4 Acids**: The oxaloacetic acid (OAA) can be converted into other 4-carbon acids, such as malate or aspartate. These 4-carbon acids are then transported to the bundle sheath cells.

4. **Decarboxylation in Bundle Sheath Cells**: In the bundle sheath cells, the 4-carbon acids are broken down through a process called decarboxylation. This reaction releases CO2 and regenerates a 3-carbon molecule (such as pyruvate).

5. **Conclusion**: The question specifically asks where the breakdown of C4 acids occurs to release CO2 and a 3-carbon molecule. This process takes place in the **bundle sheath chloroplasts**.

### Final Answer:
The correct answer is **option number two: bundle sheath chloroplasts**.

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