Question

unit 1.4 cell transport, homeostasis, feedback quiz 2025
which of the following statements about the role of phospholipids in the structure and function of biological membranes is correct?
○ phospholipids form a single layer
○ phospholipids form a structure in which the hydrophobic portion faces outward
○ phospholipids form a selectively permeable structure
○ phospholipids are completely insoluble in water

Explanation:

1. Analyze the first option: Phospholipids in biological membranes form a bilayer (two layers), not a single layer. So this option is incorrect.
2. Analyze the second option: Phospholipids have a hydrophilic (water - attracting) head and hydrophobic (water - repelling) tails. In the membrane, the hydrophilic heads face outward (toward the aqueous environment) and the hydrophobic tails face inward. So the statement that the hydrophobic portion faces outward is incorrect.
3. Analyze the third option: Phospholipids form the lipid bilayer of the cell membrane. The lipid bilayer is selectively permeable, meaning it allows some substances to pass through while restricting others. This is a key property of the cell membrane related to the structure formed by phospholipids.
4. Analyze the fourth option: Phospholipids have a hydrophilic head which is soluble in water, so they are not completely insoluble in water. This option is incorrect.

Answer:

Phospholipids form a selectively permeable structure.