Which two types of proteins are present in plasma membrane?

Explanation

### Step-by-Step Solution:

1. **Understanding Plasma Membrane**:
- The plasma membrane is a biological barrier that separates the interior of the cell from its external environment. It plays a crucial role in maintaining the cell's integrity and regulating what enters and exits the cell.

2. **Composition of Plasma Membrane**:
- The plasma membrane is primarily composed of lipids, arranged in a bilayer. The main types of lipids found in the membrane include phospholipids and cholesterol (a type of steroid).

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