In fluid mosaic model of plasma membrane ,

Options

A. upper layer is non-polar and hydrophilic
B. upper layer is polar and hydrophobic
C. phospholipids form a bimolecular layer in middle part
D. proteins form a middle layer

Answer

### Step-by-Step Solution:

1. **Understanding the Fluid Mosaic Model**:
- The fluid mosaic model describes the structure of the plasma membrane as a dynamic and flexible arrangement of various components, primarily phospholipids and proteins.

2. **Phospholipid Bilayer**:
- The plasma membrane consists of a phospholipid bilayer. Each phospholipid molecule has a hydrophilic (water-attracting) "head" and two hydrophobic (water-repelling) "tails".
- In the bilayer, the hydrophilic heads face outward towards the aqueous environment, while the hydrophobic tails face inward, away from water.

3. **Layer Characteristics**:
- The upper layer of the bilayer, which is composed of the hydrophilic heads, is indeed non-polar and hydrophilic. This means it interacts well with water.
- The lower layer also has hydrophilic heads facing inward and hydrophobic tails facing outward.

4. **Protein Distribution**:
- Proteins are embedded within the phospholipid bilayer and are classified into three types:
- **Peripheral Proteins**: Located on the surface of the membrane.
- **Integral Proteins**: Embedded within the membrane.
- **Transmembrane Proteins**: Span the entire membrane, crossing from one side to the other.

5. **Conclusion**:
- Based on the characteristics of the layers and the arrangement of proteins, the correct statement regarding the fluid mosaic model of the plasma membrane is that the upper layer is non-polar and hydrophilic.

### Final Answer:
- The correct option is: **Upper layer is non-polar and hydrophilic**.

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