Transport Across Cell Membranes. Getting things in and out of cells Part One. The cell membrane described as “semi-permeable”. It allows some substances to pass through freely, but not others. Which types of molecules can pass through the membrane?. Easily passes through:
Getting things in and out of cells
Easily passes through:
Can’t pass through:
Why is the phospholipidbilayer permeable to certain types of molecules, and not others?
Some channels are not open all the time, and have "gates" that can be opened or closed, depending on cellular conditions.
Tonicity is a relative concept. Can only use it when comparing solute concentrations.