Which of the following equations holds true for acidification reactions of CAM pathway?

Explanation

To determine which equations hold true for the acidification reactions of the CAM (Crassulacean Acid Metabolism) pathway, we need to understand the key processes involved in this pathway.

### Step-by-Step Solution:

1. **Understanding CAM Pathway**:
- The CAM pathway is a photosynthetic adaptation found in certain plants (like succulents, cacti, and pineapples) that allows them to conserve water.
- During the night, these plants open their stomata to take in carbon dioxide (CO2) and store it in the form of organic acids.

2. **Nighttime Reactions**:
- At night, phosphoenolpyruvic acid (PEP) is produced through glycolysis.
- PEP reacts with CO2 in the presence of the enzyme PEP carboxylase to form oxaloacetic acid (OAA).

3. **Formation of Malate**:
- The oxaloacetic acid then undergoes a reduction reaction catalyzed by malate dehydrogenase, converting it into malate.
- This malate can then take up hydrogen ions (H+) to form malic acid.

4. **Identifying Acidification Reactions**:
- The reactions that occur at night (acidification reactions) include:
- **Reaction 1**: PEP + CO2 + H2O → Oxaloacetic Acid (in presence of PEP carboxylase)
- **Reaction 2**: Oxaloacetic Acid → Malic Acid (in presence of malate dehydrogenase)
- Both of these reactions are considered acidification reactions because they occur during the night when CO2 is fixed and organic acids are accumulated.

5. **Deacidification Reaction**:
- During the day, the stored malic acid is converted back into pyruvic acid and releases CO2 for the Calvin cycle. This is known as deacidification and does not pertain to the acidification reactions we are focusing on.

### Conclusion:
The equations that hold true for the acidification reactions of the CAM pathway are:
- **1. PEP + CO2 + H2O → Oxaloacetic Acid**
- **2. Oxaloacetic Acid → Malic Acid**