The following theory best explains the structure of the plasma membrane :

Options

A. sandwich theory
B. fluid-mosaic theory
C. unit membrane theory
D. electrochemical theory

Explanation

**Step-by-Step Solution:**

1. **Identify the Options**: The question provides four theories regarding the structure of the plasma membrane:
- Sandwich Theory
- Fluid Mosaic Theory
- Unit Membrane Theory
- Prochemical Theory

2. **Understand Each Theory**:
- **Sandwich Theory**: This theory suggests that the plasma membrane consists of a lipid bilayer sandwiched between two layers of proteins. However, it does not accurately describe the dynamic nature of the membrane.
- **Fluid Mosaic Theory**: This theory describes the plasma membrane as a fluid structure with a mosaic of various proteins embedded in or attached to a phospholipid bilayer. It emphasizes the flexibility and the diverse arrangement of proteins.
- **Unit Membrane Theory**: This theory proposes that all biological membranes share a common structure, but it lacks detail about the specific arrangement and behavior of proteins within the membrane.
- **Prochemical Theory**: This is less commonly referenced in the context of membrane structure and does not provide a comprehensive explanation of the membrane's characteristics.

3. **Evaluate the Best Explanation**: Among the theories, the Fluid Mosaic Theory is widely accepted as it accurately describes the structure and function of the plasma membrane, highlighting the presence of both integral and peripheral proteins within the lipid bilayer.

4. **Conclusion**: The best theory that explains the structure of the plasma membrane is the **Fluid Mosaic Theory**.

**Final Answer**: The Fluid Mosaic Theory best explains the structure of the plasma membrane.

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