Glycocalyx is responsible for

Options

A. Antigens like those of blood groups ABO
B. Immune reactions and histocompatibility
C. Hormone receptors
D. All the above

Answer

**Step-by-Step Solution:**

1. **Understanding Glycocalyx**: Glycocalyx is a layer of glycoproteins and glycolipids that is found on the outer surface of the cell membrane. It is highly charged and serves as a protective barrier between the cell and its environment.

2. **Functions of Glycocalyx**:
- **Immune Response**: Glycocalyx plays a crucial role in the immune system by helping the body recognize foreign cells and pathogens. It is involved in immune reactions.
- **Histocompatibility**: Glycocalyx is also responsible for histocompatibility, which is essential for the immune system to distinguish between self and non-self cells. This is particularly important in organ transplantation.
- **Antigens**: While glycocalyx can be involved in the presentation of certain antigens, it is not specifically responsible for blood group antigens like those of the ABO system.
- **Hormone Receptors**: Glycocalyx does not primarily function as hormone receptors, although it may play a role in cell signaling.

3. **Evaluating the Options**:
- **Option 1 (Antigens like those of blood groups ABO)**: Incorrect, as glycocalyx is not responsible for blood group antigens.
- **Option 2 (Immune systems and histocompatibility)**: Correct, as glycocalyx is involved in immune reactions and histocompatibility.
- **Option 3 (Hormone receptors)**: Incorrect, as glycocalyx is not primarily responsible for hormone receptors.
- **Option 4 (All of the above)**: Incorrect, since not all statements are true.

4. **Conclusion**: The correct answer is **Option 2**, which states that glycocalyx is responsible for immune reactions and histocompatibility.

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