What are modified triglycerides with hydrophilic heads and hydrophobic tails that make up cell membranes?

Phospholipids are the correct answer because they are unique molecules that consist of a hydrophilic (water-attracting) "head" and two hydrophobic (water-repelling) "tails." This structural arrangement is crucial for the formation of cell membranes. In an aqueous environment, phospholipids naturally arrange themselves into a bilayer, with the hydrophilic heads facing outward toward the water on both sides and the hydrophobic tails tucked away from the water, leading to the formation of a semi-permeable membrane that is essential for cellular integrity and function.

This bilayer structure allows the cell membranes to maintain a distinct internal environment by regulating the movement of substances in and out of the cell. The hydrophobic tails create a barrier that prevents the passage of water-soluble molecules, while the hydrophilic heads interact with the aqueous environments both inside and outside the cell, facilitating communication and transport processes.

Other types of lipids such as steroids, triglycerides, and fatty acids do not have this specific amphipathic property that enables the formation of bilayers essential for cell membranes. Steroids are characterized by a different structure involving multiple carbon rings, triglycerides are primarily used for energy storage and consist of glycerol and three