Concentration Activity Part 2
PSI Biology
Name__________________________
Concentration Relationships
Once we have determined the concentration of any two solutions, across
a membrane, we are able to predict the diffusion of molecules. We
utilize specific terminology to characterize the relationship of
concentration between two solutions.
Isotonic, hypertonic, hypotonic solutions : The terms isotonic, hypertonic and
hypotonic are usually used in reference to cells, but are also frequently used to
compare the concentration of a solute in two solutions.
Isotonic solutions (iso means equal) Isotonic solutions are two solutions that
have the same concentration of a solute. Hypertonic solution (hyper means
above or over) A hypertonic solution is one of two solutions that has a higher
concentration of a solute. Hypotonic solution (hypo means under, beneath) A
hypotonic solution is one of two solutions that has a lower concentration of a solute.
Once we have determined, or been provided with, the concentration of two
solutions, we can identify the concentration relationship between them.
Examples:
1. A dialysis bag with a concentration of glucose = 10g/ml in placed into a beaker of
solution with a concentration of 100g/ml.
What is the concentration relationship between these two solutions?
We can state this relationship in more than one way:
The beaker solution is hypertonic to the bag solution.
OR
The bag solution is hypotonic to the beaker solution.
In most cases, you will see the relationship stated as follows:
The beaker solution is hypertonic OR the bag solution is hypotonic.
Practice:
1. When comparing two solutions we determine that solution 1 is hypertonic.
Explain what this means to the reader:
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2. Two solutions are isotonic to one another. What will be the net movement of
glucose molecules contained in both solutions and why?
Example:
Adding concentration calculations to concentration relationships:
1. The illustration below represents a lab set-up. The contents of the bag and the
beaker solutions can be found within the image labels.
20mg sucrose in
100ml water
20mg sucrose in 10ml
water
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Step one: Determine the concentration of each solution relative to sucrose.
Beaker:
Bag:
20mg sucrose
100 ml water
=
.20 g/ml sucrose
20mg sucrose
10 ml water
=
2.0 g/ml sucrose
Step two: Identify the concentration relationship between the beaker solution and
the bag solution.
The solution in the bag has a higher concentration of sucrose relative to the
beaker solution. Therefore, we can identify the bag solution as hypertonic.
OR
The solution in the beaker has a lower concentration of sucrose relative to
the bag solution. Therefore, we can identify the beaker solution as
hypotonic.
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Practice:
1. A dialysis bag has been placed into a beaker solution. The bag contains a
solution of 35g NaCl in 50ml of water. The beaker solution contains 70g of NaCl in
100 ml of water.
Complete step one:
Complete step two:
Application to osmosis and the effect on cells:
The concentration of solutions inside and outside of cells becomes critical to the
survival of cells. In addition, the permeability of the cell membrane plays a critical
role in the effect of concentration upon cells.
Utilizing the concepts of concentration relationships, we can predict how a solution
may affect a cell in a given environment.
Example:
1. A cell is placed into a hypotonic solution. Predict the effect of osmosis upon the
cell.
What we know: the solution outside of the cell has a lower concentration of solutes
and therefore a higher concentration of water, than the environment inside the cell.
Which way will the water diffuse? The net movement of water will be into the cell.
Possible effect upon the cell: The cell will swell with incoming water, possibly even
bursting, depending upon the concentration differential or gradient.
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Practice:
1. A cell is placed into a hypertonic solution. Predict the effect of osmosis upon the
cell.
What we know: the solution outside of the cell has a ____________________concentration
of solutes and therefore a ______________________ concentration of water, than the
environment inside the cell.
Which way will the water diffuse? The net movement of water will be
_____________________ the cell.
Possible effect upon the cell: The cell will _______________________water.
2. A cell is hypertonic to its environment. Predict the effect of osmosis upon the
cell.
What we know: the solution outside of the cell has a ___________________ concentration
of solutes and therefore a ________________________concentration of water, than the
environment inside the cell.
Which way will the water diffuse? The net movement of water will be
________________________the cell.
Possible effect upon the cell: The cell will ________________________ water.
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3. Consider the images seen below. Each represents a cell placed into an
environment. There is a concentration relationship between the cell and its
environment in each example. Complete the information found in the chart beneath
the set of images.
The cell has been
The cell has been
The cell has been
placed into a
placed into a
placed into a
_____________________
_____________________
_____________________
environment.
environment.
environment.
The net movement
The net movement
The net movement of
of water molecules
of water molecules
water molecules is
is ___________________
is ___________________
___________________
the cell.
the cell.
the cell.
Possible affect of
Possible affect of
Possible affect of
osmosis upon the
osmosis upon the
osmosis upon the
cell:
cell:
cell:
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