In fluid mosaic model of plasma membrane ,

Options

A. Upper layer is non- polar and hydrophilic
B. Upper layer is polar and hydrophilic
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. It was proposed by scientists Singer and Nicholson. This model illustrates how the membrane is not a rigid structure but rather fluid, allowing for the movement of various components.

2. **Components of the Plasma Membrane**: The plasma membrane is primarily composed of phospholipids. Each phospholipid molecule has a hydrophilic (water-attracting) "head" and two hydrophobic (water-repelling) "tails". In an aqueous environment, these phospholipids arrange themselves into a bilayer, with the hydrophilic heads facing outward towards the water and the hydrophobic tails facing inward, away from the water.

3. **Proteins in the Plasma Membrane**: The plasma membrane also contains proteins that are either embedded within the lipid bilayer or attached to its surface. These proteins can be classified into two categories:
- **Intrinsic (or Integral) Proteins**: These proteins span the entire membrane and are involved in various functions such as transport and signaling.
- **Extrinsic (or Peripheral) Proteins**: These proteins are attached to the exterior or interior surfaces of the membrane and play roles in signaling and maintaining the cell's shape.

4. **Correcting Misconceptions**: The question mentions incorrect statements about the nature of the layers of the plasma membrane. The upper layer is not non-polar; it is polar and hydrophilic. The hydrophobic nature refers to the tails of the phospholipids. The proteins do not form a middle layer; rather, they are interspersed throughout the phospholipid bilayer.

5. **Identifying the Correct Answer**: Based on the understanding of the fluid mosaic model and the components of the plasma membrane, the correct answer to the question is option C, which accurately reflects the structure and function of the plasma membrane.