1. To define the following terms: differential permeability, passive and active processes of transport, diffusion (simple diffusion, facilitated dif- fusion, and osmosis), solute pump, pinocytosis, and phagocytosis.
2. To describe the processes that account for the movement of sub- stances across the plasma membrane, and to indicate the driving force for each.
3. To determine which way substances will move passively through a dif- ferentially permeable membrane (given the appropriate information on concentration differences).
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The diffusion of solute particles dissolved in water through a differentially permeable membrane is called simple diffu- sion. The diffusion of water through a differentially perme- able membrane is called osmosis. Both simple diffusion and osmosis involve movement of a substance from an area of its higher concentration to one of its lower concentration, that is, down its concentration gradient.
Solute Transport Through
This computerized simulation provides information on the passage of water and solutes through semipermeable mem- branes, which may be applied to the study of transport mech- anisms in living membrane-bounded cells.
Simulating Dialysis (Simple Diffusion)
: Cell Transport Mechanisms and Per- meability from the drop-down menu and click
Watch the Cell Transport video to see an actual dialysis experiment performed. Then click
The opening screen will appear in a few seconds (Figure 1.1). The primary fea- tures on the screen when the program starts are a pair of glass beakers perched atop a solutions dispenser, a dialysis mem- branes cabinet at the right side of the screen, and a data col- lection unit at the bottom of the display.
The beakers are joined by a membrane holder, which can