Download Cellualar diffusion lab

Introduction to Design of Experiment (DOE) Lab
The purpose of this lab is to use your knowledge of cellular diffusion across a
membrane as a means to set up a two factor DOE lab.
Recall the general format for creating an experiment:
A) Observe and ask questions that lead to a problem
B) Form a hypothesis
C) Test the hypothesis
D) Analyze gathered data
E) Reject or Accept your hypothesis
F) Form a conclusion
Problem: What is the relationship between the surface area and volume of a cell as it
pertains to diffusion through its membrane? Which types of cells would yield the
fastest diffusion rate? The slowest?
Experiment: The Effects of the Size and Acid Concentration on Diffusion Time. In
short, you will be measuring how long it takes for different sizes Bromothymol Blue
Agar to change to a completely orange/yellow color.
Background:
Bromothymol blue is a pH indicator for weak acids and bases. It is mostly used in
applications that require measuring substances that would have a relatively neutral pH
(near 7), such as managing the pH of pools and fish tanks.
pH Below 6.0
pH Above 7.6
Yellow
Blue
Acetic Acid is an organic compound with the chemical formula, C2H4O2 . It is a
colorless liquid that when diluted with water is commonly called Vinegar. Vinegar is
roughly 3%-5% acetic acid by volume, making acetic acid the main component of
vinegar apart from water. Acetic acid has a distinctive sour taste and pungent smell.
The pH of 100% vinegar is about 2.4.
What types of materials do you think that you will need to perform this lab? List them
here:
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Here are the materials that you will need:
Bromothymol blue agar
Ruler
100% Acetic acid
90% Acetic acid
80% Acetic acid
Timer/stop watch
Plastic knife/scalpel (BE CAREFUL!!! This is sharp so please use caution)
Medium sized glass specimen dish
100 mL Graduated cylinder
You will be asked to cut the following dimensions of the Agar:
 1 cm x 1 cm x 1 cm
 1 cm x 1 cm x 8 cm
 2 cm x 2 cm x 2 cm
You will have three choices of vinegar solutions to use:
 100%
 90%
 80%
Based on your knowledge of a DOE which do you think will be the high (+1), low (-1)
and standard values in numbers 6&7? Fill your answers in Table 1 below
Table 1
Factors Used in Experiment
(-)
Standard
(+)
(-)
Standard
(+)
What is the response variable for this experiment?
What is the possible interaction effect?
What is your hypothesis? Write in specific terms of each variable.
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Procedures:
Each group will randomly be assigned one of the seven parts of the DOE. Cut one agar
shape designated by the label on the specimen dish. CUT AS ACCURATELY AS
POSSIBLE.
1. Pour 200 mL of vinegar into specimen dish.
2. Immerse one cube in the acetic acid, start the timer.
3. Observe the cube, noting observations as the blue core “disappears”.
4. When the cube is void of blue, stop and record the time in seconds.
Randomization:
How should we go about randomizing this?
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Which one did your group get? One of the three standards? (+,+)?(+,-)?(-,+)?(-,)?
Observations:
Table 2
Cell Diffusion Observations
Trial
Observations
Size of cell:
Who measured acetic acid:
Who cut it:
Who timed:
Observations made during trial:
Write a sample anchor here:
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Data:
Table 2
Cell Diffusion Data
Trial
Surface Area (cm2)
Volume (cm3)
SA:V ratio
Time (s)
Write a sample anchor here:
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What are some possible sources for error in this lab design?
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Fill in the blanks to complete the sample title for the lab report.
An Investigation of the Effects of _________________ and __________________ on the
Use all of this information to do a write up of this lab. 
Be sure to include whether or not you accepted or rejected your hypothesis. Don’t
forget to include a conclusion. (In other words, you are doing an MMSTC lab write up)
Below is a table of the three DOEs. You will need to fill in this table so that you can do
the math to analyze the data.
9A Results
Order
Runs
Stand
++
- Stand
+ - +
Stand
9B Results
Result
Order
Runs
Stand
++
- Stand
+ - +
Stand
9C Results
Result
Order
Runs
Stand
++
- Stand
+ - +
Stand
Result