Question 8

The majority of the human cell membrane comprises a phospholipid bilayer.

The human cell membrane is primarily made up of a phospholipid bilayer, which forms the fundamental structure that provides both a barrier and a medium for various cellular functions.

A) Phospholipid bilayer

This option is correct as the phospholipid bilayer constitutes the backbone of the cell membrane. It consists of two layers of phospholipids that create a semi-permeable membrane, crucial for maintaining the integrity of the cell and facilitating the transport of substances in and out of the cell.

B) Protein

While proteins are essential components of the cell membrane, they do not comprise the majority of its structure. Proteins serve various functions, including signaling and transport, but the predominant structural feature is the phospholipid bilayer.

C) Ergosterol

Ergosterol is a sterol found in fungal cell membranes and is not a significant component of human cell membranes. Therefore, this option is incorrect as it does not contribute to the majority of the membrane's structure in human cells.

D) Cholesterol

Cholesterol is present in the cell membrane and plays a role in maintaining fluidity and stability, but it is not the major component. The majority structure remains the phospholipid bilayer, making this option incorrect.

Conclusion

The phospholipid bilayer is the primary structural component of the human cell membrane, providing both a barrier and a platform for protein function. While proteins, ergosterol, and cholesterol play important roles, they do not constitute the majority of the membrane's structure, which is firmly established by the phospholipid bilayer.