Transmembrane proteins in cell membrane are

Options

A. intrinsic proteins
B. extrinsic proteins
C. glycocalyx
D. tunnel proteins

Answer

**Step-by-Step Text Solution:**

1. **Understanding Transmembrane Proteins**: Transmembrane proteins are a specific type of protein that spans the entire width of the cell membrane. They are embedded within the lipid bilayer and extend from one side of the membrane to the other.

2. **Classification of Proteins**: Proteins associated with the cell membrane can be classified into two main categories: intrinsic (or integral) proteins and extrinsic (or peripheral) proteins. Intrinsic proteins are embedded within the membrane, while extrinsic proteins are attached to the exterior or interior surfaces of the membrane.

3. **Identifying Transmembrane Proteins**: Transmembrane proteins are a subtype of intrinsic proteins. They are characterized by their ability to span the membrane and are involved in various functions, including acting as gateways for molecules to enter or exit the cell.

4. **Functions of Transmembrane Proteins**:
- They facilitate the transport of specific substances across the membrane.
- They can also play a role in signaling and communication between the cell and its environment.

5. **Examples of Transmembrane Proteins**: A well-known example of a transmembrane protein is aquaporins, which are channels that allow for the selective transport of water molecules across the cell membrane.

6. **Conclusion**: Based on the classification and functions of transmembrane proteins, the correct answer to the question is that transmembrane proteins in the cell membrane are intrinsic proteins.

**Final Answer**: The correct option is **intrinsic proteins**.

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