In Cell 1,

Question

Consider the following plant cells floating in an open beaker containing 0.2M sucrose. By definition, an open beaker has a pressure potential 0 MPa. Assume that the cells have come to equilibrium with the solution in the beaker.







A.  ?p = 0.0 MPa and ?w = 0.0 MPa.

B.  ?p = 0.0 MPa and ?w = -1.0 MPa.

C.  ?p = +0.5 MPa and ?w = -0.5 MPa.

D.  ?p = -0.5 MPa and ?w = -0.5 MPa.

E.  ?p = 0.0 MPa and ?w = +0.5 MPa.



Clarify Question

What is the key concept addressed by the question?

What type of thinking is required?

What key words does the question contain and what do they mean?

 

Gather Content

What do you already know about water potential? How does it relate to the question?

 

Consider Possibilities

What other information is related to the question? Which information is most useful?



Choose Answer

Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?



Reflect on Process

Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

 

Answer 1

C.  ?p = +0.5 MPa and ?w = -0.5 MPa.

Clarify Question
What is the key concept addressed by the question?
        · The key concept in this question is water potential.
What type of thinking is required?
                o You are being asked to take what you already know and use, or apply, it to water potential in a cell.
What key words does the question contain and what do they mean?
        · Water potential, which refers to the potential energy of a solution.
        · Pressure potential, which is the outward pressure exerted by the water in a cell.
        · Solute potential, or the pressure that is a result of the solute molecules that are present.
 
Gather Content
What do you already know about water potential? How does it relate to the question?
        · Water potential is equal to solute pressure plus pressure potential.
        · Solute potential is always negative.
        · As solute increases, solute potential decreases.
        · Decreasing solute potential causes a decrease in water potential.
 
Consider Possibilities
What other information is related to the question? Which information is most useful?
        · Recall that numerically solute potential and pressure potential must together equal water potential.

Choose Answer
Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        · In cell 1, the solute potential is given as -1.0MPa. To solve this problem, you must select a choice that takes this given solute concentration into consideration. There is only one choice in which water potential equals the sum of solute potential and pressure potential.

Reflect on Process
Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        The question is asking you to deduce the water potential and pressure potential for a given cell, given the solute potential. If you arrived at the correct answer, well done! If you came up with an incorrect answer, where did the process break down? Did you remember that water potential must equal the sum of pressure potential and solute potential?