Solved by a verified expert:Comparative Cell Membranes
and Transport
Hands-On Labs, Inc.
Version 42-0033-00-02
Lab Report Assistant
This document is not meant to be a substitute for a formal
laboratory report. The Lab Report Assistant is simply a summary of the
experiment’s questions, diagrams if needed, and data tables that should be
addressed in a formal lab report. The intent is to facilitate students’ writing
of lab reports by providing this information in an editable file which can be
sent to an instructor.
Exercise 1: Plant Cells and
Osmosis
Data Table 1. Potato Masses.
Test
Tube
Solution
Initial
Mass (g)
Final
Mass (g)
Mass
Difference (g)
Percent
Change in Mass (%)
Class
Average: Percent Change in Mass (%)
(If
Available)
a
Distilled water
b
0.2 M sucrose
c
0.4 M sucrose
d
0.6 M sucrose
e
0.8 M sucrose
f
1.0 M sucrose
Hypothesis:
Data
Table 2.
Graph of Potato Mass versus Solution.
Mass vs. Solution
Questions
A. Define osmosis. How did you observe osmosis
in Exercise 1?
B. List molar concentrations (0.0 M, 0.2 M, etc.)
at which water entered the potato strips. Why did water move into the potato
strips? Were these solutions hypotonic, hypertonic, or isotonic?
C.
List the molarities at which water exited the potato strips. Why did
water move out of the potato strips? Were these solutions hypotonic,
hypertonic, or isotonic?
D. Was the hypothesis
you recorded in Data Table 1
supported or refuted by your experimental results? Discuss your results in
relation to your hypothesis. (It is acceptable if your hypothesis was refuted,
as long as you can explain WHY.)
E. If you were asked to place potato strips in
a solution that would cause the potato to neither gain or lose mass, what
molarity would you choose and why? Would this solution be hypotonic,
hypertonic, or isotonic?
Exercise 2: Diffusion and
Temperature
Data Table 3.Diffusion of KMnO4.
Solution
Temperature (°C)
Initial Observations (0 minutes)
Observations After 5 Minutes
Observations After 10 Minutes
Cold
Ambient
Warm
Questions
A.
How does temperature affect the rate of diffusion?
Use your experimental results to support your answer.
B.
If potassium permanganate was placed in a solution
of boiling water (100°C), would the rate of diffusion be greater than diffusion
in cold water? Would diffusion of potassium permanganate in boiling water be
greater than diffusion in warm water?
C.
Why does temperature affect the rate of diffusion?
(Hint: Consider the relationship between
temperature and the speed at which particles move.)
Exercise
3: Diffusion across a Membrane
Data Table 4.Dialysis Membrane and Starch.
Substance
Initial observations
Final observations
Solution in Dialysis Tubing
Solution in Cup 1
Data Table 5.Dialysis Membrane and Sugar.
Test Tube
Substance
Initial Observations
Final Observations
1
Solution outside of dialysis tubing (cup
1)
2
Solution in dialysis tubing (cup 2)
3
Distilled water
Questions
A. Define diffusion.
B. IKI indicator tests for the presence of
which substance? Benedict’s reagent tests for the presence of which substance?
C. In the first part of Exercise 3, a glucose/starch
solution was placed in dialysis tubing. Then, the tubing was placed in a cup
containing IKI indicator. Did starch stay within the tubing or move out of the
tubing? Did IKI indicator stay in the solution in the cup or move into the
tubing? Support your answer with the observations you recorded in Data Table 3.
D. In the second part of Exercise 3, the IKI
solution in the cup and the contents of the dialysis tubing were heated with
Benedict’s reagent. Did sugar stay within the dialysis tubing or move out of
the tubing? Support your answer with the observations you recorded in Data Table 4.
E. What was the purpose of testing distilled water
with Benedict’s reagent?
F. How is a cell membrane similar to the
dialysis tubing used in this experiment?
G. Is the movement of substances in this
exercise active or passive?
H. From your data, might it be inferred that
a) starch and glucose molecules are the same size, b) starch molecules are
larger than glucose molecules, or c) starch molecules are smaller than glucose
molecules. Use your data to explain your answer.
I.
Could the speed at which molecules diffused over the dialysis tubing
been slowed down or sped up? If so, explain how.
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