How many layers does membrane have by unit membrane structure?

Explanation

To answer the question about how many layers the membrane has according to the unit membrane structure, we can break down the explanation as follows:

### Step-by-Step Solution:

1. **Understanding the Unit Membrane Concept**: The unit membrane concept was introduced by Robertson. It describes the structure of biological membranes.

2. **Composition of the Membrane**: According to this concept, the biological membrane is primarily composed of a lipid bilayer. This lipid bilayer consists of phospholipids, which have hydrophilic (water-attracting) heads and hydrophobic (water-repelling) tails.

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