Final answer:
The lipid ends of phospholipids are called hydrophobic, meaning they repel water. These molecules are amphipathic, with a hydrophilic head and a hydrophobic tail, and form the lipid bilayer that is essential for cell membrane structure. The correct option is 1) Hydrophilic
Step-by-step explanation:
The lipid ends of phospholipids are called hydrophobic, which means they are 'water-fearing' and do not mix well with water. Phospholipids are amphipathic molecules, consisting of a hydrophilic (water-loving) 'head' and a hydrophobic 'tail'.
When phospholipids are placed in water, they spontaneously arrange themselves into a lipid bilayer, with the hydrophobic tails facing inward, away from the water, and the hydrophilic heads facing outwards, interacting with the water.
This arrangement is crucial for the structure of cell membranes, providing a barrier that separates the interior of the cell from the external environment. The correct option is 1) Hydrophilic