Which of these is not correct regarding ribosomes ?

Options

A. Non-membrane bound
B. Present in the cytoplasm and on RER
C. Absent in chloroplast and mitochondria
D. Take part in protein synthesis

Explanation

To determine which statement regarding ribosomes is incorrect, let's analyze each statement step by step.

### Step-by-Step Solution:

1. **Identify the Characteristics of Ribosomes:**
- Ribosomes are known as non-membrane bound organelles. They do not have a surrounding membrane, which is a key characteristic.

2. **Location of Ribosomes:**
- Ribosomes can be found in the cytoplasm as free ribosomes or attached to the rough endoplasmic reticulum (RER). This indicates that they are indeed present in both locations.

3. **Presence in Organelles:**
- Ribosomes are also present in mitochondria and chloroplasts. Specifically, they contain 70S ribosomes in these organelles, which are involved in protein synthesis.

4. **Analyzing the Statements:**
- **Statement 1:** "Ribosomes are non-membrane bound organelles." - This statement is correct.
- **Statement 2:** "They are present in cytoplasm and on the rough endoplasmic reticulum." - This statement is also correct.
- **Statement 3:** "They are absent in chloroplast and mitochondria." - This statement is incorrect because ribosomes are indeed present in both chloroplasts and mitochondria.
- **Statement 4:** "They take part in photosynthesis." - While ribosomes are involved in protein synthesis, they do not directly take part in the process of photosynthesis itself.

5. **Conclusion:**
- The statement that is not correct regarding ribosomes is **Statement 3**: "They are absent in chloroplast and mitochondria."

### Final Answer:
The statement that is not correct regarding ribosomes is: **They are absent in chloroplast and mitochondria.**

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