Select the incorrect statement .

Options

A. The cell envelope consists of a tightly bound three layered structure , of which plasma membrane is the innermost layer
B. A specialized differentiated from of cell membrane called mesosome is the characteristic of prokaryotes.
C. Surface structures of the bacteria , like flagella , pili and fimbriae play a major role in motility .
D. Gas vacuoles are found in blue green and purple and green photosynthetic bacteria.

Answer

To solve the question of selecting the incorrect statement regarding bacterial cell structures, let's analyze each option step by step:

### Step 1: Analyze the First Statement
**Statement:** The cell envelope consists of a tightly bound three-layered structure of which the plasma membrane is the innermost layer.

**Analysis:** This statement is correct. The cell envelope of bacteria indeed consists of three layers: the outermost layer is the glycocalyx, the middle layer is the cell wall, and the innermost layer is the plasma membrane.

### Step 2: Analyze the Second Statement
**Statement:** The mesosome is a specialized differentiated form of the cell membrane and is a characteristic of prokaryotes.

**Analysis:** This statement is also correct. Mesosomes are indeed specialized structures that arise from the plasma membrane in prokaryotic cells and are involved in various functions such as cell division.

### Step 3: Analyze the Third Statement
**Statement:** The surface structures of the bacteria like flagella, pili, and fimbriae play a major role in motility.

**Analysis:** This statement is incorrect. While flagella are responsible for the motility of bacteria, pili and fimbriae do not contribute to motility. Instead, pili are primarily involved in conjugation (transfer of genetic material), and fimbriae are used for attachment to surfaces.

### Step 4: Analyze the Fourth Statement
**Statement:** Gas vacuoles are found in blue-green and purple-green photosynthetic bacteria.

**Analysis:** This statement is correct. Gas vacuoles are indeed present in photosynthetic bacteria, helping them maintain buoyancy in aquatic environments.

### Conclusion
The incorrect statement among the options provided is the third one, which suggests that pili and fimbriae play a major role in motility.

### Final Answer
**The incorrect statement is:** The surface structures of the bacteria like flagella, pili, and fimbriae play a major role in motility.

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