A Scientist isolated the plasma membrane from some animal cells and put them in a solution of chemicals that stabilised the membranes. When she added a small amount of a salt solution, she discovered that although the membranes seemed intact, the amount of protein in the stabilising solution had increased. These new proteins in the stabilising solution were probably

Options

A. (a) peripheral proteins
B. (b) integral proteins
C. (c) lipid-anchored proteins
D. (d) trimeric G proteins.

Answer

To solve the question regarding the proteins that increased in the stabilizing solution after adding a salt solution to the isolated plasma membrane, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Plasma Membrane Structure**:
The plasma membrane is primarily composed of a phospholipid bilayer with various proteins embedded within it. These proteins can be classified into integral proteins (which span the membrane) and peripheral proteins (which are associated with the membrane surface).

**Hint**: Recall the fluid mosaic model of the plasma membrane, which describes its structure and the types of proteins present.

2. **Identify the Role of Salt Solution**:
The addition of a salt solution increases the ionic strength of the environment. This can disrupt the interactions between peripheral proteins and the lipid bilayer, allowing these proteins to be released into the solution.

**Hint**: Consider how ionic strength affects protein interactions with membranes.

3. **Differentiate Between Protein Types**:
- **Integral Proteins**: These are embedded within the membrane and are not easily removed by mild treatments.
- **Peripheral Proteins**: These are loosely attached to the membrane surface and can be detached with mild treatments, such as exposure to salt solutions.

**Hint**: Think about which proteins are more likely to be affected by changes in ionic strength.

4. **Conclusion**:
Given that the scientist observed an increase in protein concentration in the stabilizing solution after adding the salt solution, it is most likely that the proteins released were peripheral proteins. These proteins are soluble in aqueous solutions and can be easily separated from the membrane under such conditions.

**Hint**: Remember that peripheral proteins are often referred to as extrinsic proteins and are typically found on the membrane's surface.

### Final Answer:
The new proteins in the stabilizing solution were probably **peripheral proteins** (Option A).