According to unit membrane structure, the thickness of plasma membrane is about

Options

A. a) `35 Å`
B. b) `20 Å`
C. c) `75 Å`
D. d) `100 Å`

Explanation

To determine the thickness of the plasma membrane according to the unit membrane structure, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Unit Membrane Model**: The unit membrane model, proposed by Robertson, describes the plasma membrane as consisting of a bimolecular lipid layer sandwiched between two layers of proteins.

2. **Identify the Components**: According to the model:
- There is one lipid layer in the center.
- There are protein layers on both the inside and outside of the lipid layer.

3. **Determine the Thickness of Each Component**:
- The thickness of each protein layer is approximately **20 Ångström** (Å).
- The thickness of the lipid layer is approximately **35 Ångström**.

4. **Calculate the Total Thickness**:
- Since there are two protein layers (one on each side of the lipid layer), we add their thickness:
- Thickness from protein layers: \(20 Å + 20 Å = 40 Å\)
- Now, add the thickness of the lipid layer:
- Total thickness = Thickness of protein layers + Thickness of lipid layer
- Total thickness = \(40 Å + 35 Å = 75 Å\)

5. **Conclusion**: Therefore, the total thickness of the plasma membrane is **75 Ångström**.

### Final Answer:
The thickness of the plasma membrane according to the unit membrane structure is **75 Ångström**.

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