What else can the equations tell us?
Here are a few last questions on interpreting the equations:
What will the rate of water flow be if permeability is zero?
- I need a hint ... : Permeability is Pwater.
- ...another hint ... : Zero times anything is zero.
I think I have the answer: No matter how high the difference in osmolarity, no osmosis will occur if the permeability is 0. For example, osmosis will not work through a brick wall
When will the rate of water flow be the highest?
- I need a hint ... : the product of three quantities is maximized when each quantity is maximized
I think I have the answer: First, you need the permeability to be as high as possible. Secondly, you need the difference in osmolarity to be as high as possible. So, if OsM A=0 (pure water) and OsM B was as high as possible, then the rate of water will be maximized
What happens if the osmolarity of the two solutions is the same?
- I need a hint ... : If the osmolarities are the same, what about the concentrations?
I think I have the answer: If OsM B = OsM A,
B - OsM A) = 0, so NO net osmosis will take place, no matter how large or
leaky your membrane.
None of these were really rocket science. The point is that the equation for rate of water flow is simply a formalization of what our intuition tells us should happen. The equation puts intuition into mathematical language!
Copyright University of Maryland, 2007
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