Which of the following pair lack the unit membrane

Options

A. Nucleus and ER
B. Mitochondria and Chloroplast
C. Ribosome and nucleolus
D. Golgi body and lysosome

Answer

To determine which pair lacks a unit membrane, we need to analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding Unit Membrane**: A unit membrane is a biological membrane that consists of a lipid bilayer with associated proteins. Organelles like the nucleus, mitochondria, and chloroplasts have unit membranes.

2. **Option 1: Nucleus and Endoplasmic Reticulum (ER)**:
- The nucleus is surrounded by a nuclear envelope, which is a double membrane structure.
- The endoplasmic reticulum (ER) is also a membrane-bound organelle.
- **Conclusion**: Both the nucleus and ER have unit membranes. Therefore, this option is incorrect.

3. **Option 2: Mitochondria and Chloroplast**:
- Mitochondria are double membrane-bound organelles, consisting of an outer and inner membrane.
- Chloroplasts also have a double membrane structure.
- **Conclusion**: Both mitochondria and chloroplasts have unit membranes. Therefore, this option is incorrect.

4. **Option 3: Ribosome and Nucleolus**:
- Ribosomes are not membrane-bound; they are composed of RNA and proteins and can be found freely in the cytoplasm or attached to the ER.
- The nucleolus is a dense region within the nucleus where ribosomal RNA is synthesized, and it does not have a surrounding membrane.
- **Conclusion**: Both ribosomes and nucleolus lack unit membranes. Therefore, this option is correct.

5. **Final Answer**: The pair that lacks a unit membrane is **Ribosome and Nucleolus**.