According to widely accepted "Fluid mosaic model" cell membranes are semi-fluid, where lipids and integral proteins can diffuse randomly. In recent years, this model has been modified in several repects. In this regard, which of the following statements is incorrect

Options

A. Proteins in cell membranes can travel within the lipid bilayer
B. Proteins can remain confined within certain domains of the membrane
C. Proteins can also undergo flip-flop movements in the lipid bilayer
D. Many proteins remain completely embedded within the lopid bilayer

Answer

To solve the question regarding the fluid mosaic model of cell membranes and identify the incorrect statement, we will analyze each of the provided options step by step.

### Step-by-Step Solution:

1. **Understanding the Fluid Mosaic Model**:
- The fluid mosaic model, proposed by Singer and Nicholson in 1972, describes the structure of the plasma membrane as a fluid combination of lipids and proteins. The lipids form a bilayer, while proteins float in or on this bilayer, leading to a mosaic-like appearance.

2. **Analyzing the Options**:
- **Option A**: "Proteins in cell membrane can travel within lipid bilayer."
- This statement is correct. Integral proteins can move laterally within the lipid bilayer, allowing for fluidity in the membrane.

- **Option B**: "Proteins can remain confined within certain domains of the membrane."
- This statement is also correct. Some proteins are indeed confined to specific areas or domains within the membrane, which helps in organizing membrane functions.

- **Option C**: "Proteins can also undergo flip-flop movements in the lipid bilayer."
- This statement is incorrect. While lipids can undergo flip-flop movements, proteins are generally restricted to their domains and do not flip-flop across the bilayer due to their size and the nature of the lipid bilayer.

- **Option D**: "Many proteins remain completely embedded within the lipid bilayer."
- This statement is correct. Integral proteins can be fully embedded in the lipid bilayer, either partially or completely.

3. **Identifying the Incorrect Statement**:
- Based on the analysis, the incorrect statement is **Option C**: "Proteins can also undergo flip-flop movements in the lipid bilayer."

### Final Answer:
The incorrect statement regarding the fluid mosaic model is **Option C**: "Proteins can also undergo flip-flop movements in the lipid bilayer."