Pyrenoid consists of

Options

A. Starch around protein
B. Protein around starch
C. Protein only
D. Starch only.

Answer

**Step-by-Step Solution:**

1. **Understanding Pyrenoid**:
- Pyrenoids are subcellular structures found in certain algae and some land plants, such as hornworts. They play a crucial role in the storage and metabolism of carbohydrates.

2. **Composition of Pyrenoid**:
- Pyrenoids consist of a central protein body. This protein body is surrounded by starch granules. Therefore, the key component of the pyrenoid is protein, with starch being present around it.

3. **Analyzing the Options**:
- The options provided are:
- A) Starch on protein
- B) Protein around starch
- C) Protein only
- D) Starch only
- Based on the composition of pyrenoids, we can eliminate options A, C, and D:
- A) Incorrect because starch is not on protein; rather, starch surrounds protein.
- C) Incorrect because pyrenoids are not made up of protein only; they also contain starch.
- D) Incorrect as pyrenoids do not consist of starch only; they have a protein core.

4. **Correct Answer**:
- The correct answer is **B) Protein around starch**. This accurately describes the structure of the pyrenoid, where the protein body is central and surrounded by starch.

5. **Conclusion**:
- Pyrenoids are essential for carbohydrate storage and play a role in carbon fixation, confirming their importance in the physiology of certain plant groups.