4. Which of the following best explains how molecules such as O, and CO, can move across the membrane of a cell?
A. The majority of the cell membrane contains protein channels that allow this type of
molecule into the cell.
B. The majority of the cell membrane is nonpolar, which allows small, nonpolar
molecules to freely cross.
C. The phospholipids of the membrane are tightly packed, so only small molecules and
ions can fit between phospholipids