What type of compound is primarily responsible for organic cellular membrane structure?

Lipids are the primary compounds responsible for organic cellular membrane structure. The cell membrane, or plasma membrane, is composed mainly of a bilayer of phospholipids, which have a hydrophilic (water-attracting) head and two hydrophobic (water-repelling) tails. This unique structure allows the membrane to form a barrier that separates the interior of the cell from the external environment while allowing selective permeability.

Additionally, proteins are embedded within the lipid bilayer and play vital roles in membrane functions, such as transport, signaling, and structural support, but the foundational structure itself is predominantly made of lipids. Carbohydrates are often attached to lipids and proteins on the outer surface of the membrane and are involved in cell recognition and signaling, but they do not form the basic structure of the membrane. Vitamins, while important for various biological processes, do not contribute to the structural framework of cellular membranes. Thus, lipids are essential for maintaining the integrity and functionality of cell membranes.