Final answer:
The outer portion of the cell membrane is polar and attracts water due to its hydrophilic nature, while the internal portion is nonpolar and repels water, being hydrophobic. The term 'amphipathic' refers to the dual characteristics of phospholipids, making them essential for forming the cell membrane.
Step-by-step explanation:
The structure of a cell membrane is critical to its function, with phospholipids playing a key role. The correct answer to the student's question is 'a) attracts, repels', meaning the outer portion of the membrane is polar and attracts water, while the internal portion is nonpolar and repels water.
Phospholipid molecules, which are amphipathic, have a polar (hydrophilic) head that is water-loving and a nonpolar (hydrophobic) tail that is water-fearing. When these molecules organize into a bilayer to form a cell membrane, the hydrophilic heads face outward towards the aqueous environment on both sides of the membrane, while the hydrophobic tails point inward, away from the water. This arrangement creates a hydrophilic exterior and a hydrophobic interior within the cell membrane.
Thus, the membrane's exterior attracts and interacts favorably with water, whereas the interior repels water, preventing it from passing freely through the membrane, which is crucial for cellular function.