Cell recognition and adhesion are facilitated by components of plasma membrane. These components are generally

Options

A. protein molecules alone
B. lipids alone
C. both lipids and proteins
D. glycolipids and glycoproteins.

Explanation

**Step-by-Step Solution:**

1. **Understanding Cell Recognition and Adhesion**:
- Cell recognition refers to the ability of cells to identify and interact with each other, which is crucial for various biological processes such as immune response and tissue formation.
- Cell adhesion is the process by which cells attach to each other or to the extracellular matrix, which is essential for maintaining the structure and function of tissues.

2. **Components of the Plasma Membrane**:
- The plasma membrane is composed of various molecules, including lipids, proteins, and carbohydrates. Among these, certain components play a significant role in cell recognition and adhesion.

3. **Role of Glycolipids**:
- Glycolipids are lipids with carbohydrate chains attached to them. They are found on the outer surface of the plasma membrane.
- These carbohydrate chains can act as recognition sites for specific molecules, facilitating cell-cell interactions.

4. **Role of Glycoproteins**:
- Glycoproteins are proteins that have carbohydrate groups attached to them. Like glycolipids, they are also present on the outer surface of the plasma membrane.
- Glycoproteins serve as receptors that can bind to specific signaling molecules, allowing cells to communicate and adhere to each other.

5. **Mechanism of Action**:
- The specific shapes of glycoproteins and glycolipids allow them to interact with other cells or molecules, enabling the recognition and adhesion processes.
- These interactions can trigger various cellular responses, including signaling pathways that lead to changes in cell behavior.

6. **Conclusion**:
- In summary, the components of the plasma membrane that facilitate cell recognition and adhesion are primarily glycolipids and glycoproteins.

**Final Answer**: Glycolipids and glycoproteins are the components of the plasma membrane that facilitate cell recognition and adhesion.

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