The unique uneconomical process which is mediated by RuB CO is

Options

A. respiration
B. photorespiration
C. photosynthesis
D. transpiration

Answer

**Step-by-step Solution:**

1. **Understanding Rubisco**: The enzyme in question is Ribulose 1,5-bisphosphate carboxylase/oxygenase, commonly known as Rubisco. It plays a crucial role in the process of carbon fixation during photosynthesis.

2. **Identifying the Processes**: The question asks about a unique uneconomical process mediated by Rubisco. The options provided are:
- Respiration
- Photorespiration
- Photosynthesis
- Transpiration

3. **Analyzing Each Option**:
- **Respiration**: This is a general term applicable to both plants and animals, involving the consumption of oxygen and release of carbon dioxide. It is not specific to Rubisco.
- **Photosynthesis**: This process involves the conversion of light energy into chemical energy, resulting in food production. It is a highly economical process for plants.
- **Transpiration**: This refers to the loss of water vapor from plant surfaces, particularly through stomata. It does not involve Rubisco directly.
- **Photorespiration**: This process occurs when Rubisco reacts with oxygen instead of carbon dioxide, leading to the production of a two-carbon compound instead of a three-carbon compound, which is less efficient. This process is considered uneconomical because it does not lead to the production of glucose.

4. **Conclusion**: Given that photorespiration is a process mediated by Rubisco that occurs under conditions of low carbon dioxide and high oxygen, and it is less efficient in terms of energy production, the correct answer to the question is **photorespiration**.

**Final Answer**: The unique uneconomical process which is mediated by RuBisco is **photorespiration**.

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