The selectively permeable nature of cell membrane is mainly contributed by

Options

A. Lipids
B. Proteins
C. Lipo-proteins
D. Carbohydrates

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the main contributor to the selectively permeable nature of the cell membrane. Selectively permeable means that the membrane allows certain substances to pass through while restricting others.

2. **Identifying Components of Cell Membrane**: The cell membrane is primarily composed of phospholipids, which form a bilayer. This bilayer is crucial for the membrane's selective permeability.

3. **Analyzing the Options**:
- **Lipids**: While the membrane is made of lipids (specifically phospholipids), they alone do not account for the selective permeability.
- **Proteins**: Membrane proteins play a significant role in transport and signaling, but they are generally larger and more complex than the molecules that can easily pass through the membrane.
- **Lipoproteins**: These are complexes of lipids and proteins. They can facilitate the transport of lipids in the bloodstream and may assist in selective permeability, but they are not the primary structural component of the membrane.
- **Carbohydrates**: These are involved in cell recognition and signaling but do not contribute directly to the permeability of the membrane.

4. **Conclusion**: The selectively permeable nature of the cell membrane is mainly attributed to the presence of proteins that facilitate the transport of specific molecules. However, the question specifically asks for the main contributor, which leads us to conclude that lipoproteins, being a combination of lipids and proteins, are significant in this context.

5. **Final Answer**: The selectively permeable nature of the cell membrane is mainly contributed by **lipoproteins**.

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