Fluid mosaic model for the structures of plasma membrane explains

Options

A. a single lipid layer in between 2 protein layers
B. a layer of proteins on one sides and a bilayer lipid on other side
C. 2 lipid layers and 1 protein Layer
D. a middle phospholipid bilayer with proteins both inside and on outer side of lipids bilayer

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, including lipids and proteins. This model emphasizes that the membrane is not a static structure but rather a fluid one where components can move laterally within the layer.

2. **Identifying the Components**: The plasma membrane is primarily composed of a phospholipid bilayer. Each phospholipid molecule has a hydrophilic (water-attracting) head and two hydrophobic (water-repelling) tails. This arrangement allows the formation of a bilayer, where the hydrophilic heads face outward towards the aqueous environment, and the hydrophobic tails face inward, away from water.

3. **Role of Proteins**: Within this phospholipid bilayer, various proteins are embedded. These proteins can be classified as intrinsic (integral) proteins, which span the membrane, and extrinsic (peripheral) proteins, which are attached to the outer or inner surfaces of the membrane. These proteins serve various functions, including transport, signaling, and acting as receptors.

4. **Analyzing the Options**:
- Option A: "A single lipid layer in between two protein layers" - This does not accurately represent the bilayer structure.
- Option B: "A layer of proteins on one side and a bilayer lipid on the other side" - This is also incorrect as it does not account for the bilayer arrangement.
- Option C: "Two lipid layers and one protein layer" - This is misleading as it implies a different arrangement than what is present in the fluid mosaic model.
- Option D: "A middle phospholipid bilayer with proteins both inside and on outer sides of the lipid bilayer" - This accurately describes the fluid mosaic model, where proteins are embedded within and attached to the phospholipid bilayer.

5. **Conclusion**: Based on the analysis of the options and understanding of the fluid mosaic model, the correct answer is option D: "A middle phospholipid bilayer with proteins both inside and on outer sides of the lipid bilayer."

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