In the context of the lipid bilayer, what is the hydrophilic head of a phospholipid primarily made of?

• A. A phosphate-containing polar group attached to glycerol
• B. A polymer of amino acids forming a polar peptide headgroup
• C. A cholesterol ring structure with a short hydrocarbon tail
• D. Two nonpolar fatty acid hydrocarbon chains

Answer: (A)

Verified step by step guidance

1. Understand the structure of a phospholipid, which is a major component of the lipid bilayer in cell membranes.
2. Recall that a phospholipid molecule has two main parts: a hydrophilic (water-attracting) head and hydrophobic (water-repelling) tails.
3. Identify that the hydrophilic head contains a phosphate group, which is polar and interacts well with water.
4. Recognize that this phosphate group is attached to a glycerol backbone, forming the polar head region of the phospholipid.
5. Contrast this with the hydrophobic tails, which are composed of two nonpolar fatty acid hydrocarbon chains, not part of the head.