Question 29

The cellular membrane consists of a bilayer of phospholipids.

The cellular membrane is primarily composed of a bilayer of phospholipids, which form the fundamental structure that provides both barrier and fluidity to the membrane.

A) Nucleic acids

Nucleic acids, such as DNA and RNA, are not components of the cellular membrane. They are primarily involved in genetic information storage and transmission rather than forming structural components of membranes.

B) Phospholipids

Phospholipids are indeed the main constituents of the cellular membrane, forming a bilayer that allows for selective permeability and fluidity. This bilayer structure is essential for the membrane's functional properties, including the regulation of substance entry and exit.

C) Proteins

While proteins are integral to the function of cellular membranes, they do not form the bilayer itself. Instead, they are embedded within or attached to the lipid bilayer, serving roles in signaling, transport, and structural support.

D) Carbohydrates

Carbohydrates are not a structural component of the membrane bilayer. They are typically found on the exterior surface of membranes, often attached to proteins or lipids, where they play roles in cell recognition and signaling.

Conclusion

Phospholipids are the correct answer as they form the bilayer structure of cellular membranes, providing essential properties for membrane function. All other options, while relevant to cellular components or functions, do not comprise the bilayer itself and therefore do not answer the question correctly.