Number of water molecule (s) required for each `CO_2` during carboxylation reaction in `C_3` cycle is

Options

A. 6
B. zero
C. 12
D. 1

Answer

To determine the number of water molecules required for each carbon dioxide molecule during the carboxylation reaction in the C3 cycle, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the C3 Cycle**: The C3 cycle, also known as the Calvin cycle, is a series of biochemical reactions that take place in the chloroplasts of C3 plants. It is responsible for the fixation of carbon dioxide (CO2) to produce glucose.

2. **Carboxylation Reaction**: In the carboxylation phase of the C3 cycle, carbon dioxide is fixed to a 5-carbon sugar (ribulose bisphosphate, RuBP) to form a 6-carbon intermediate, which is then split into two 3-carbon molecules (3-phosphoglycerate, 3-PGA).

3. **Requirement of Carbon Dioxide**: For the synthesis of one molecule of glucose, six molecules of carbon dioxide are required. This is a fundamental aspect of the C3 cycle.

4. **Water Molecules Requirement**: Each carbon dioxide molecule requires water for the process of photosynthesis. Specifically, during the light-dependent reactions, water molecules are oxidized to provide electrons needed for the reduction of carbon dioxide.

5. **Calculation of Water Molecules**: Since six molecules of carbon dioxide are used to produce one molecule of glucose, and each carbon dioxide molecule requires one water molecule for the process, we conclude that six molecules of water are needed for the six molecules of carbon dioxide.

6. **Final Answer**: Therefore, the number of water molecules required for each carbon dioxide molecule during the carboxylation reaction in the C3 cycle is **6**.