Final answer:
O2 and CO2 cross the cell membrane through passive diffusion due to concentration gradients, while glucose uses facilitated diffusion, and H2O can diffuse or use aquaporins. No energy is required for these processes. The correct option is C.
Step-by-step explanation:
The substances CO2, O2, glucose, and H2O each cross the cell membrane through different mechanisms:
- O2 and CO2 are gases that can pass through the cell membrane via passive diffusion. Oxygen typically moves into cells since it's more concentrated outside, and carbon dioxide moves out of cells because it's produced inside the cell and generally more concentrated there.
- Glucose, being a larger and polar molecule, cannot diffuse freely across the lipid bilayer. Instead, it is transported across the membrane through a process called facilitated diffusion using carrier proteins or transporters that do not require energy.
- H2O (water), although polar, is small enough to pass through the cell membrane via special protein channels known as aquaporins or through the lipid bilayer by passive diffusion due to its polarity and partial charge, making it somewhat soluble in the lipid bilayer.
Passive diffusion does not require energy as it moves substances from an area of higher concentration to an area of lower concentration, in contrast to active transport mechanisms that require cellular energy. The correct option is C.