In fluid mosaic model of plasma membrane ,

Options

A. Upper layer is non-polar and hydrophilic
B. Polar layer is 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 of cells. It was proposed by scientists Singer and Nicholson in 1972.
- This model illustrates that the cell membrane is composed of a double layer (bilayer) of phospholipids with proteins embedded within it.

2. **Components of the Plasma Membrane:**
- The plasma membrane consists of two main components: lipids (specifically phospholipids) and proteins.
- Phospholipids have a hydrophilic (water-attracting) "head" and two hydrophobic (water-repelling) "tails". This arrangement forms a bilayer.
- Proteins can be classified as integral proteins (spanning the membrane) and peripheral proteins (attached to the surface).

3. **Structure of the Bilayer:**
- In the bilayer, the hydrophilic heads face outward towards the aqueous environment, while the hydrophobic tails face inward, away from water. This creates a barrier that is selectively permeable.

4. **Analyzing the Options:**
- The question provides statements about the fluid mosaic model. We need to evaluate each statement:
- "Upper layer is nonpolar, hydrophilic": This is incorrect; the upper layer (the phosphate heads) is polar and hydrophilic.
- "Polar layer is hydrophobic": This is also incorrect; the polar layer is hydrophilic.
- "Phospholipids make up a bimolecular layer in the middle part": This is correct; the bilayer is formed by phospholipids.
- "Proteins form the middle layer": This is incorrect; proteins are embedded within the phospholipid bilayer, not forming a separate middle layer.

5. **Conclusion:**
- The correct statement regarding the fluid mosaic model is that "Phospholipids make up a bimolecular layer in the middle part."

**Final Answer:**
- The correct answer is: "Phospholipids make up a bimolecular layer in the middle part."

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