Diffusion, osmosis, and tonicity

Movement Across Membranes (videos - Active and passive transport & osmosis):

1 - Passive processes - require no expenditure of energy by a cell:

Animated gif showing the process of osmosis

 

2 - Active processes - require the expenditure of energy by cells:

 
Active transport

Animated gif showing the action of the sodium-potassium pump
Active Transport: The Sodium-Potassium Pump

Used with permission of Gary Kaiser

 


Endo- and exocytosis

Animated gif showing the process of phagocytosis
Used with permission of Gary Kaiser

 

An example of endocytosis (by a white blood cell called a neutrophil)


 

Video: Red blood cells in iso-, hyper-, and hypotonic solutions (and www. sciencephoto.com)

Dialysis tubing experiments

Review questions:

What is the difference between passive and active processes? What is simple diffusion & what factors influence the rate of simple diffusion? What is osmosis? Be able to explain the process of osmosis. What is facilitated diffusion? What is a carrier? What is active transport? Which of these processes require energy? Which require carriers? Are carriers specific? Which of these processes can move substances from areas of lower concentration to areas of higher concentration? What is exocytosis, endocytosis? Do exocytosis & endocytosis require energy? What is a solute, solvent, solution? What's the definition of concentration? What is an isotonic solution, hypertonic solution, hypotonic solution? What would happen to a cell placed in an isotonic solution, hypertonic solution, hypotonic solution? What is crenation? What is lysis? Dialysis tubing experiments: What will happen to the liquid level if (1) a more concentrated sucrose solution is put in the dialysis tubing, and (2) distilled water is put in the dialysis tubing and sucrose solution in put in the beaker? Why?