2.6 Water Movement: Osmosis, Tonicity, and Osmoregulation
The diffusion of free water across a selectively permeable membrane, whether artificial or cellular, is called osmosis.
To Think About:
What are the different ways to describe the relative tonicity of environments? How do differences in osmolarity impact the movement of water in a cell? How does the constant movement of molecules across a membrane maintain growth and homeostasis? What is osmoregulation and how does it contribute to the health and survival of organisms? How does water potential impact the movement of water? How does solute potential impact the movement of water? How do organisms maintain water balance?
Watch: AP Daily Video Tonicity and Osmoregulation
Answer the Following Questions:
- What is osmosis?
- Water is a polar molecule, so how do large quantities of water get across the phospholipid bilayer?
- Explain the difference between a solute and a solvent.
- The total solute concentration in a solution is called ___________________
- What is tonicity?
- How are water concentrations and solute concentrations related to each other?
- Water diffuses from a _________________ environment into a ______________________ environment.
- Explain how water moves in a dynamic equilibrium.
- In plant cells, environmental hypertonicity results in ____________________, which results in water _____________________ the cell.
- In plant cells, environmental hypotonicity results in _____________________, which results in water ____________________ the cell.
- Explain why a plant cell does not lyse/explode when in environmental hypotonicity.
- In animal cells, environmental hypertonicity results in a cell that is _____________
- In animal cells, environmental hypotonicity results in a cell that is _____________
- How does a paramecium avoid lysis in a hypotonic environment?
Watch: AP Daily Video Tonicity and Osmoregulation (Graphing)
Answer the Following Questions:
- What are the components of an effective graph mentioned in the video?
- Describe the most common use for each of the following types of graphs: a. Line graph b. Scatterplot c. Histogram d. Bar graph e. Box and whisker plot f. Dual Y
- What types of graphs are used in the practice problems in this video?
Watch: AP Daily Video Tonicity and Osmoregulation (Water Potential)
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Answer the Following Questions:
- What does water potential measure?
- What are the two components of water potential?
- Water moves from areas of____________________water potential to areas of____________________water potential.
- The value of water potential can be____________________, ____________________, or____________________.
- What is the water potential of pure water?
- How does increasing the amount of solute affect water potential?
- What does an ionization constant tell you?
- What is C?
- In water potential calculations, what units (Fahrenheit, Celsius or Kelvin) must be used for temperature?
- What is the water potential of a 0.5 M sucrose solution at 21 degrees Celsius in an open system?
- What is the pressure potential in an open system?
Supplementary Resources:
Georgia State University Hyperphysics: Diffusion and Osmosis (from a physicist’s point of view)
Wisc-Online: Passive Transport-Osmosis (simulation)
