Cell membrane is a vital component of all living cells and plays a crucial role in various cellular processes. It is a selectively permeable barrier that separates the internal cellular environment from the external surroundings. The cell membrane is composed of a phospholipid bilayer embedded with various proteins, including enzymes. These enzymes are responsible for catalyzing specific biochemical reactions within the cell membrane.

The number of enzymes present in the cell membrane can vary depending on the type of cell and its specific function. While there is no fixed number of enzymes in the cell membrane, it is estimated that there are approximately 30 enzymes present in the cell membrane of eukaryotic cells. Therefore, the correct answer to the given question is option 'B' - 30.

Explanation:
1. Cell membrane composition:
The cell membrane is primarily composed of phospholipids, which form a bilayer structure. These phospholipids have hydrophilic (water-loving) heads and hydrophobic (water-hating) tails. The hydrophilic heads face the aqueous environment both inside and outside the cell, while the hydrophobic tails are sandwiched between the heads, forming a barrier.

2. Proteins in the cell membrane:
Embedded within the phospholipid bilayer are various proteins that perform important functions. These proteins can act as receptors, channels, transporters, and enzymes. Enzymes in the cell membrane are responsible for catalyzing specific chemical reactions, playing a crucial role in cellular processes.

3. Functions of membrane enzymes:
The enzymes present in the cell membrane perform a wide range of functions. They can be involved in signal transduction pathways, membrane transport, cell adhesion, and cell signaling. For example, enzymes such as phospholipases are involved in the breakdown of phospholipids, while ATPases are responsible for transporting ions across the membrane.

4. Number of enzymes in the cell membrane:
The number of enzymes in the cell membrane can vary depending on the cell type and its specific functions. While there is no fixed number, it is estimated that there are approximately 30 enzymes present in the cell membrane of eukaryotic cells.

Conclusion:
The cell membrane is a complex structure composed of phospholipids and proteins. Among these proteins, enzymes play a crucial role in various cellular processes. While the exact number of enzymes in the cell membrane may vary, it is estimated to be around 30 in eukaryotic cells.