BIOL 2401 Laboratory
Lab Report 1
Membrane Transport Mechanisms Exercise 5B Activities 1 - 5
The first lab report will be a guided report to teach you the proper format and
expectations for future reports. Fill in each section with the requested information.
Please type the completed document, using this sheet as a template. Papers not
typed will not be accepted for grading. Take advantage of tools such as spell check
and grammar check on the word processor.
Lab report 1 is due no later than Thurs, Jan 31 at the beginning of your lab. Lab
reports WILL NOT BE ACCEPTED LATE. (If you are wise, you won’t wait until
the night before this is due, since this activity will help you prepare for your test…)
Introduction: (Write a 1 – 2 page introduction giving background information relevant to
the lab activities. You should include a discussion of cell membrane structure, the nature
of polar and non-polar molecules and ions, the concept of selective permeability,
concentration gradients, the importance of membrane transport to living cells, the
different types of membrane transport, etc. followed by a brief summary of the purpose of
the experiment to be done. In addition, any terms or abbreviations to be used in the
report should be defined and explained in the introduction (e.g. MWCO: what does it
stand for and what is its significance? Osmotic pressure: what is it and what is its
significance?). Use your own words to define the terms as often as you can, and be
sure to cite any references when you use someone else’s words.
After your introduction, you will treat each activity separately. For activities 1, 2, 3 & 5,
answer the following questions using the data gathered in the activity. Include a copy of
the data tables generated as a part of your report.
Activity 1
What is the relationship of pore size to permeability?
Is the membrane equally permeable to all the tested substances?
Were there any substances to which the membrane was not permeable? Why?
What is the relationship between the data from activity 1 and the mechanism of diffusion
in living cells?
Activity 2
What is the role of the carrier proteins in this experiment?
Does concentration gradient play a role in facilitated diffusion?
What is the relationship between the data from activity 2 and the mechanism of facilitated
diffusion in living cells?
Activity 3
Explain the relationship between solute concentration and osmotic pressure.
Is osmotic pressure generated if solutes are able to diffuse?
In what ways are osmotic pressures important to living cells?
Activity 5
What is relationship between ATP and the Na+-K+ pumps?
Why does transport rate sometimes stop before the ions are completely transported?
What factors determine the rate of active transport?
What is the relationship between the data from activity 5 and the mechanism of facilitated
diffusion in living cells?
For Activity #4 ONLY: Prepare a formal lab report using the following guidelines as a
template.
Step #1 is the Introduction. You’ve already done that at the beginning of this
assignment.
Step #2 is the Hypothesis
Create a hypothesis for activity #4. Remember that a hypothesis is to be tested, and
should be based on knowledge already obtained in other experiments. A hypothesis
should always require more than a “yes” or “no” answer. To say “I think that some items
will filtered and others won’t” is NOT a valid hypothesis. To give you a start, I have
created a hypothesis for ACTIVITY #1. It is NOT a hypothesis for #4, but it should help
you create a proper hypothesis.
Example for activity 1: The relative pore size of the membrane will determine its
permeability to various substances. The rate of diffusion for each substance will be
determined by both pore size and the concentration gradient.
Step #3 is the Procedure
The procedure as listed in the lab manual. Write each step as if completing the
experiment in a real lab using real lab equipment and solutions. The words “Click on”
should not appear in your procedure! For example, Activity 4 Step 2 should read “Obtain
solutions of the following solutes at a 5 mg/ml concentration: NaCl, Urea, Glucose,
Powdered Charcoal. Dispense the solutions into the top beaker.”
Step #4 Data
A data table of the results of the activity should follow the procedure list. DO NOT just
print out the data from the CD or website. There are many bugs still to be worked out,
and many times data is lost or is non-decipherable. Instead, use the data tables from page
P-11, preferably created with the word processor or a spreadsheet. Less desirably, you
may photocopy the completed data table, then cut and paste the table into the appropriate
area of your lab report.. Everything you need to formulate a conclusion should be found
in the introduction paragraph and data tables.
Step #5 Graph
Graph the data in your table to show the movement of each substance over time. If you
use a spreadsheet (Excel) to create your data table, the spreadsheet will be able to
construct an appropriate graph for you. The x-axis will be time and the y-axis will be
concentrations. You’ll have a line for each substance in the mixture.
Step #5 Data Analysis and Conclusion:
Use the questions on page P-11 to guide your thinking as you compose a paragraph or
two describing the outcome of the experiment. A proper conclusion should be more than
“My hypothesis was true” or “My hypothesis was false”. Instead, you should describe
what you learned about Filtration based on the data you gathered. Looking at the graph
will help you. This data will either support or negate your hypothesis, but there is no
need to formally state this. Instead, explain (don’t just list….) any discrepancies that
exist between your hypothesis and the actual outcome based on the data.