In contact with water, phospholipids produce

Options

A. Monolayer
B. Bilayer
C. Trilayer
D. Emulsion.

Answer

To solve the question "In contact with water, phospholipids produce," we need to understand the structure and behavior of phospholipids when they interact with water.

### Step-by-Step Solution:

1. **Understanding Phospholipids**:
- Phospholipids are molecules that consist of a hydrophilic (water-attracting) "head" and two hydrophobic (water-repelling) "tails." The head is made up of a phosphate group, while the tails are typically composed of fatty acids.

2. **Behavior in Water**:
- When phospholipids come into contact with water, they do not remain as individual molecules. Instead, they arrange themselves in a specific way due to their dual nature (hydrophilic head and hydrophobic tails).

3. **Formation of Structures**:
- In an aqueous environment, the hydrophilic heads of phospholipids face outward towards the water, while the hydrophobic tails orient inward, away from the water. This arrangement minimizes the exposure of the hydrophobic tails to water.

4. **Resulting Structure**:
- This orientation leads to the formation of a **bilayer** structure, where two layers of phospholipids are formed. The hydrophilic heads are on the outer sides (facing the water), and the hydrophobic tails are tucked inside, away from the water.

5. **Conclusion**:
- Therefore, when phospholipids are in contact with water, they produce a **bilayer**. This bilayer is fundamental in the formation of cell membranes.

### Final Answer:
The correct answer is **bilayer**.

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