Singer and Nicholson's model of plasma membrane differs from Robertson's model in the

Options

A. Number of lipid layers
B. Arrangement of proteins
C. Arrangement of lipid layers
D. Absence of protein layers

Answer

To answer the question about how Singer and Nicholson's model of the plasma membrane differs from Robertson's model, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding the Models**:
- **Singer and Nicholson Model**: This model is known as the fluid mosaic model. It describes the plasma membrane as a flexible structure with various proteins embedded within or associated with a fluid lipid bilayer.
- **Robertson Model**: This model suggests that the plasma membrane consists of two continuous layers of proteins surrounding a lipid bilayer.

2. **Key Features of Each Model**:
- In the **Singer and Nicholson model**, proteins can be of two types:
- **Intrinsic proteins** (integral proteins) that span the membrane.
- **Extrinsic proteins** (peripheral proteins) that are attached to the surface of the membrane.
- In the **Robertson model**, the proteins form two distinct layers (one on each side of the lipid bilayer) and do not mix with the lipids.

3. **Comparison of Protein Arrangement**:
- The **Singer and Nicholson model** emphasizes a more dynamic arrangement where proteins can move laterally within the lipid bilayer, contributing to the fluid nature of the membrane.
- The **Robertson model** presents a more static view, where proteins are fixed in place and do not exhibit lateral movement.

4. **Conclusion**:
- The main difference between the Singer and Nicholson model and the Robertson model lies in the **arrangement of proteins** in relation to the lipid bilayer. The Singer and Nicholson model describes a fluid arrangement, while the Robertson model describes a more rigid structure.

### Final Answer:
The Singer and Nicholson's model of plasma membrane differs from Robertson's model in the **arrangement of the lipid bilayer and proteins**.

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