What is the true of fluid mosaic model?

Options

A. Phospholipid monlayer is present over protein layer
B. Phospholipid bilayer is present over protein layer
C. Protein embedded in phospholipid bilayer
D. Phospholipid layer is sandwitched between two protein layers.

Answer

### Step-by-Step Solution:

1. **Understanding the Fluid Mosaic Model**: The fluid mosaic model is a widely accepted representation of the structure of the cell membrane, proposed by scientists Singer and Nicholson in 1972. This model describes the cell membrane as a dynamic and flexible structure.

2. **Structure of the Cell Membrane**: According to the fluid mosaic model, the cell membrane is primarily composed of a phospholipid bilayer. Each phospholipid molecule has a hydrophilic (water-attracting) head and two hydrophobic (water-repelling) tails, which allows them to arrange themselves into a bilayer.

3. **Role of Proteins**: The model also states that various proteins are embedded within this phospholipid bilayer. These proteins can be intrinsic (integral) proteins that span across the membrane or extrinsic (peripheral) proteins that are located on the surface.

4. **Correct Option Identification**:
- **Option A**: "Phospholipid monolayer is present over lipid layer" - Incorrect, as the membrane consists of a bilayer, not a monolayer.
- **Option B**: "Phospholipid bilayer is present over protein layer" - Incorrect, as proteins are embedded within the bilayer, not layered over it.
- **Option C**: "Protein embedded in phospholipid bilayer" - Correct, as proteins are indeed embedded within the phospholipid bilayer.
- **Option D**: "Phospholipid layer is sandwiched between two protein layers" - Incorrect, as there is no defined protein layer; proteins are randomly distributed within the bilayer.

5. **Conclusion**: The true statement regarding the fluid mosaic model is that "proteins are embedded in the phospholipid bilayer."