Two molecules of the primary acceptor of carbon dioxide in Calvin cycle undergoes photorespiration. How many glycine molecules will be formed from it ?

Options

A. 1
B. 2
C. 3
D. 4

Answer

To solve the question, we need to understand the process of photorespiration and how it relates to the Calvin cycle in plants, particularly C3 plants.

### Step-by-Step Solution:

1. **Understanding the Calvin Cycle**:
- The Calvin cycle is a series of biochemical reactions that take place in the chloroplasts of photosynthetic organisms. The primary acceptor of carbon dioxide in the Calvin cycle is Ribulose bisphosphate (RuBP).

2. **Photorespiration Process**:
- Photorespiration occurs when the concentration of oxygen is higher than that of carbon dioxide, leading to the oxygenation of RuBP instead of carboxylation. This process is more pronounced in C3 plants.

3. **Formation of Glycine**:
- During photorespiration, one molecule of RuBP is converted into one molecule of 3-phosphoglycerate (3-PGA) and one molecule of phosphoglycolate (2-PG).
- The phosphoglycolate is then converted through a series of reactions into glycine. Specifically, two molecules of phosphoglycolate are converted into two molecules of glycine.

4. **Calculating Glycine from Two RuBP**:
- Since the question states that two molecules of the primary acceptor (RuBP) undergo photorespiration, we can analyze the outcome:
- Each molecule of RuBP leads to the formation of two molecules of glycine.
- Therefore, for two molecules of RuBP, the total glycine produced will be:
\[ 2 \text{ RuBP} \times 2 \text{ glycine per RuBP} = 4 \text{ glycine molecules} \]

5. **Conclusion**:
- Thus, the total number of glycine molecules formed from two molecules of RuBP undergoing photorespiration is **4**.

### Final Answer:
The answer is **4** glycine molecules.