AAMC FL Practice Exam

Phospholipids consist of which components?

1. One phosphate, one glycerol, and two fatty acids

2. One glycerol, two phosphates, and two fatty acids

3. Three fatty acids and one phosphate group

4. Two phosphate groups and one glycerol

The correct answer is: One phosphate, one glycerol, and two fatty acids

Phospholipids are essential components of cell membranes and play a crucial role in cellular structure and function. The correct structure of a phospholipid includes one glycerol molecule, one phosphate group, and two fatty acid chains. The glycerol acts as a backbone to which the phosphate group and fatty acids are attached. The phosphate group is usually charged at physiological pH, making that region hydrophilic (water-attracting), while the two fatty acid tails are hydrophobic (water-repelling). This amphipathic nature—having both hydrophilic and hydrophobic parts—allows phospholipids to spontaneously form bilayers in aqueous environments, a fundamental characteristic of cell membranes. The other options do not accurately represent the structure of phospholipids. They may include incorrect ratios or components that do not align with what defines phospholipids. For instance, having more than one phosphate group would not fit the typical structure, as would having three fatty acids instead of just two. Understanding this configuration is key to grasping how phospholipids function in biological membranes.