Water and the Plant Cell
Goals and Objectives
 

1. Be able to describe what hydrogen bonding is and how it helps to explain the unique physical and chemical properties of water.
2. Be able to explain how osmosis is a special case  of diffusion.
3. Be able to distinguish between osmotic pressure and osmotic potential.
4. Be able to describe the concept of water potential and how it is related to the chemical potential of water.
5. Be able to explain how the concept of water potential is used to predict the movement of water in a plant.
6. Be able to describe the importance of turgor pressure in a plant.  Be able to relate this to what occurs in animals.

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Study Questions:
 

1. Describe the structure of a water molecule.  Be sure to explain how partial charges on the atoms lead to eletronegative and electropositive atoms, and the polar molecule.
2. What is a hydrogen bond?  How much energy is contained in a hydrogen bond?
3. What is a hydration shell?  Why are hydration shells important biologically?
4. Describe each of the following thermal properties of water, and give an example of why the property is important biologically.  Also, relate how hydrogen-bonding is responsible for these unique water properties.
• Temperature and Physical State
• Absorption and Dissipation of Heat
• melting and Vaporizing Water
5. Why is water the universal solvent?
6. What is a hydration shell and why is it important in dissolving substances?
7. What does the dielectric constant of a molecule describe?  What can it tell us about the ability of molecules to cross membranes?
8. What is the difference between cohesion and adhesion?
9. How does cohesion affect water's surface tension and tensile strength?
10. Movement of substances from one place to another is called translocation.  How is water translocated in a plant?
11. Describe what occurs in the bulk flow of water.  Give an example.
12. Describe what occurs in diffusion.   How do molecules diffuse?  Give an example.
13. F= -DADC/l (see textbook, equation #2.1)  What does this equation describe?  What are the individual components of this equation?
14. Diffusion of water is a special case called _______.  When two chambers are separated from one another by a ________ _________ _________.
15. Describe what the osmotic pressure is and indicate the symbol used for osmotic pressure in mathematical equations.
16. How does the osmotic pressure of a solution relate to the osmotic potential?  What is the symbol used to indicate osmotic potential in mathematical equations?
17. How does osmotic potential, chemical potential, and pressure potential affect water movement in a plant?