How Do Molecules Enter
Cells…Part II
Student learning targets:
after this investigation you will be able to
• Plan and conduct a scientific investigation, choosing
a method appropriate to the question being asked.
• Collect, analyze, and display data using calculators
• Draw conclusions supported by evidence from the
investigation and consistent with established
scientific knowledge.*c
• Give examples of common solutions.
• Describe the structure of the cell membrane and
how the membrane regulates the flow of materials
into and out of the cell.
• Provide practical examples of how this knowledge
can be applied.
• Survivorman (4:15, 4:25)
Survival Brainstorm
• Imagine that you are on a stranded life raft in the
middle of the ocean like the previous video clip.
• Write down at least two primary needs that
need to be taken care for your survival.
• Pair-share your ideas with a neighbor. Classshare.
• Lets focus on Water…Write down how long do
you think you could survive without water on the
raft?
Remember?
• What were the molecules that we were dealing
with in our Dialysis Tube Lab?
• IKI, starch, glucose, water
• Which one of the molecules did we not have
evidence of it moving across the Dialysis Tube
Membrane?
• Water!!
Water
• Write at least two reasons why you think
water is important for your body.
• Pair-share then Class-share
• If you could not find fresh water would it be a
good idea to drink the salt water surrounding
the life raft? Why or why not?
Salt Water…What is it?
• Suppose you are making salt water…write
what is dissolving the salt?
• This is called a solvent.
• Whenever you have a solid, like salt, that is
being added to water it is called a solute.
• When a solvent and a solute are combined
you now have a solution…so see if you have
a solution to this question…
– salt water is a ________________? 
Let’s see how well you can concentrate…
• You take a 200 mL water sample from the mouth of the
Snoqualmie river where it meets the ocean, the ocean
itself, and the headwater of the Snoqualmie…rank in
order which body of water has the most salt, and
WHY?
• The amount of a solute dissolved in a solvent in a fixed
volume is known as its concentration. The
concentration of a solution can be measured in ppm
(parts per billion), ppb, % concentration, Molarity or
g/L.
• Review your ranked order from the example above and
now explain “why” in terms of the concept of
concentration..
Back to the dialysis tube investigation
• How could you test for whether or not water
moved into or out of the dialysis tube
membrane? _________________________
Investigation question: does solute
concentration effect the movement of
water into or out of cells?
• Write your hypothesis: - remember this is a
testable statement
• Write your prediction: If, then, because
statement.
• What would be the
– manipulated-include all treatments
– responding and
– controlled (at least 3) variables of this
investigation be?
Responding variable- what are you
measuring?
• Here is an example of change in
mass…between Coleen and Jerry who would
win this weeks weigh off in the Biggest Loser
and WHY?
• That’s right…Coleen would barely win with a
weight loss of 4.6% versus 4.5% for
Jerry…how do we calculate % loss?
% Change (∆)
• [(mass final - mass initial) / (mass initial) ] x 100
• What is Ed’s % Change for this episode of Biggest Loser?
• What is Aubrey’s % change in weight?
• Did you include the negative symbol in front
of the value?
[(mass final – mass initial) / (mass initial) ]
x 100%
• 203 lbs. - 200lbs. = 1.5%
200 lbs.
Manipulated variable and levels of
treatment.
Controlled variables?
Procedure
• Lab Groups 1-6: Use 0.0M & 0.2M Sucrose Solution
• Lab Groups 7-11: Use 0.4M & 0.6M Sucrose Solution
• Lab Groups 12-16: Use 0.8M & 1.0M Sucrose Solution
Procedure:
1. Gather 2 clear plastic cups & four pieces of potato core
2. Label Solute Concentration and group initials on the cups using the white
3. Completing the Virtual Cell Internet
stickers at your tableWorksheet: ____/10
3. Fill cups with 50mL with the assigned solutions
4. Using the scales at your table mass (and record) two potato pieces and
place in your first solution. Then repeat for your second solution.
5. Place cups in designated area to sit for a 24 hour period.
Create the following Data Table: