Final answer:
A lipid made of a glycerol molecule with two fatty acids and a phosphate group forming a 'head' is called a phospholipid, essential for cell membrane structure.
Step-by-step explanation:
The correct answer to the student's question is: a) Phospholipid. A phospholipid is a type of lipid molecule that is a critical component of all cell membranes. It consists of a three-carbon glycerol backbone with two fatty acid molecules attached to the first and second carbons, and a phosphate-containing group attached to the third carbon. This structure results in a molecule with a hydrophilic (water-attracting) head and two hydrophobic (water-repelling) tails, making the phospholipid amphiphilic or "dual-loving." Examples of phospholipids include Phosphatidylcholine and Phosphatidylserine, both essential for forming the bilayer structure of cell membranes, where the hydrophilic heads face the aqueous environment and the tails face each other inside the bilayer.