Which statement describes the structure of a phospholipid?

A phospholipid is a crucial component of cell membranes and is characterized by its unique structure, which contains one hydrophilic head and two hydrophobic tails. The hydrophilic head is attracted to water, making it polar, while the two hydrophobic tails are repelled by water, making them nonpolar. This dual nature allows phospholipids to form bilayers in an aqueous environment, creating the basic structure of biological membranes.

This arrangement is essential for creating a barrier that protects the cell and regulates the movement of substances in and out of the cell. The presence of two tails allows for a more stable bilayer formation compared to having just one tail. Additionally, the hydrophilic heads face outward towards the watery environments both inside and outside the cell, while the hydrophobic tails align inward, away from water, resulting in the formation of a semi-permeable membrane.

The other options, which suggest more heads or a structure made entirely of amino acids or a rigid backbone, do not accurately describe the structure of phospholipids and would not correctly explain the properties and functions that they serve within biological systems.