[Campbell Biology P.181] Which types of molecules can easily pass through the lipid bilayer ... | Practice Question

Which types of molecules can easily pass through the lipid bilayer of a cell membrane without the aid of membrane proteins?

  • A: Small, nonpolar molecules like O2 and CO2.
  • B: Large, polar molecules like glucose.
  • C: Charged ions like Na+ and Cl-.
  • D: Water molecules.

Explanation

The text states that nonpolar molecules such as hydrocarbons, CO2, and O2 are hydrophobic and can therefore dissolve in the lipid bilayer and cross it easily without the aid of membrane proteins. In contrast, polar molecules, charged ions, and even water pass slowly or are impeded by the hydrophobic interior.