Final answer:
A phospholipid consists of a hydrophilic head region and a hydrophobic tail region, and these molecules are amphipathic. The structure of phospholipids is key to the formation of cellular membranes. The correct option is A.
Step-by-step explanation:
The molecule that consists of a hydrophilic "head" region and a hydrophobic "tail" region is a phospholipid. A phospholipid molecule is composed of a hydrophilic head, which includes a phosphate group attached to a glycerol molecule. The tails are hydrophobic, made up of two fatty acids, and are long hydrocarbon chains.
The interaction between the hydrophilic heads and hydrophobic tails with the aqueous environment is what leads to the formation of biological membranes, where the hydrophilic heads face out towards the water and the hydrophobic tails face inward, away from the water.
Molecules that contain both polar (water-attracting) and nonpolar (water-repelling) regions, like phospholipids, are referred to as amphipathic.
This characteristic is essential for the formation of cellular membranes, with phospholipids aligning in a bilayer, creating a semipermeable membrane that is fluid and dynamic thanks to the unique properties of the phospholipid molecules. The correct option is A.