In Singer and Nicolson's model of plasma membrane, the extrinsic proteins are

Options

A. Tightly associated with intrinsic protein and can be easily separated
B. Loosely associated with intrinsic protein
C. Loosely associated with intrinsic protein and can be easily separated
D. Loosely associated with intrinsic protein and cannot be easily separated

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the nature of extrinsic proteins in the Singer and Nicolson model of the plasma membrane.

2. **Identifying the Model**: The Singer and Nicolson model, proposed in 1972, is also known as the fluid mosaic model of the plasma membrane. This model describes the structure of the plasma membrane as a mosaic of various components, including lipids and proteins.

3. **Types of Proteins**: In this model, proteins are categorized into two types: intrinsic (or integral) proteins and extrinsic (or peripheral) proteins.

4. **Characteristics of Extrinsic Proteins**: Extrinsic proteins are defined as proteins that are loosely bound to the surface of the lipid bilayer of the membrane. This means they are not embedded within the lipid bilayer like intrinsic proteins.

5. **Separation of Extrinsic Proteins**: Because extrinsic proteins are loosely associated with the membrane, they can be easily separated from it. This is a key characteristic that distinguishes them from intrinsic proteins, which are tightly bound to the membrane.

6. **Evaluating Options**: When looking at the options provided in the question:
- The first option states that extrinsic proteins are tightly associated, which is incorrect.
- The second option might suggest they are loosely associated, which is correct.
- The third option correctly states that they are loosely associated with intrinsic proteins and can be easily separated.
- The fourth option states they cannot be easily separated, which is also incorrect.

7. **Conclusion**: The correct answer is that extrinsic proteins are loosely associated with the membrane and can be easily separated.

**Final Answer**: In the Singer and Nicolson model of the plasma membrane, the extrinsic proteins are loosely associated with the membrane and can be easily separated.

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