Which one statement regarding plasma membrane is correct ?

Options

A. It outer and inner layer is electron-dense while the middle layer is electron transparent .
B. Its outer and middle layer is electron transparent while the inner layer is electron -dense.
C. Its outer and inner layer is electron transparent while the middle one is electron-dense.
D. All layers are electron -dense.

Answer

To determine which statement regarding the plasma membrane is correct, we need to analyze the structure and properties of the plasma membrane.

### Step-by-Step Solution:

1. **Understanding the Structure of the Plasma Membrane**:
- The plasma membrane is primarily composed of a phospholipid bilayer. This bilayer consists of two layers of phospholipids, where the hydrophilic (water-attracting) heads face outward towards the aqueous environment, and the hydrophobic (water-repelling) tails face inward, away from water.

2. **Electron Density in the Plasma Membrane**:
- The plasma membrane can be described in terms of electron density. The outer and inner layers of the membrane are electron-dense due to the presence of lipids and proteins. The middle layer, which is less dense, is often referred to as electron transparent because it contains fewer electrons compared to the outer and inner layers.

3. **Evaluating the Statements**:
- **Option 1**: "Outer and inner layer of electron dense while the middle layer is electron transparent."
- This statement is correct as it accurately describes the electron density of the layers of the plasma membrane.
- **Option 2**: "Outer layer and middle layer is electron transparent."
- This statement is incorrect because the outer layer is electron dense.
- **Option 3**: "Outer and inner is electron transparent while middle layer is electron dense."
- This statement is incorrect as both the outer and inner layers are electron dense.
- **Option 4**: "All layers are electron dense."
- This statement is misleading because the middle layer is considered electron transparent.

4. **Conclusion**:
- The correct statement regarding the plasma membrane is **Option 1**: "Outer and inner layer of electron dense while the middle layer is electron transparent."