To
encourage
more student-active learning in my upper-level cell physiology course, I
redesigned the laboratory component of the course to include
student-designed
experiments to be performed by the class as a whole. Small groups of
students
cooperatively designed original experiments and led the class in performing
the
exercises. To help the students
make necessary decisions and choices, I provided them with some parameters
for
their experiments. I advised
them
that the experiments should elucidate some aspect of cell biology, use a
methodology or equipment available in our department, be performed in a
two-hour
laboratory period, and be designed and presented by a group of three to four
students.
The class
was
composed of 15 undergraduate students in their senior year.
There were seven Sports Biology majors, three Biology majors, and one
Chemistry/Biology major. There
were
four self-selected groups.
These
students had all taken at least one laboratory course per semester
throughout
their college career.
There were
twelve laboratory periods scheduled during the semester.
The first eight periods were spent in a traditional laboratory
format.
Students were given written introductory material containing
abbreviated
background information, technical procedures to be followed, and questions
to be
answered after completing the exercise. These
exercises were planned to illustrate concepts that had been discussed in
lecture
and to familiarize students with various laboratory techniques used in cell
biology. Weekly exercises were chosen to provide students hands-on
experience with a relatively large selection of methods from which to choose
for
their own experiments. The last
four weeks of the semester were devoted to the presentation of
student-designed
experiments (one per week).
Before the
final month of the course, students had practiced protein gel
electrophoresis,
enzymatic assays using spectrophotometry, cellular fractionation using
differential centrifugation, isolation of red blood cells, separation of
water-soluble and lipid cellular components, phospholipid separation using
thin
layer chromatography, quantification of phospholipids based on the
construction
of a standard concentration curve, and the measurement of aerobic metabolism
in
isolated tissues.
Some
lecture
time was devoted to planning and preparation for the experiments.
Early in the semester the class compiled a list of characteristics of
a
good experimental design. They
decided that a good lab exercise should:
1. Be easy to follow
2. Have a definite result
3. Have the preparatory work completed in
advance
4. Allow some room for error
5. Be able to be completed within the allotted
time
of a laboratory period
6. Be based on background information provided
by
the instructor
Another
lecture
period was spent examining a variety of laboratory manuals (from
introductory
biology courses and cell/molecular biology courses) to seek feasible
procedures,
applicable background information, preparatory instructions, etc.
A subsequent lecture period was spent
perusing chemical catalogs for the necessary supplies in appropriate
amounts at affordable prices. Supplies were ordered based on the students’
calculations and recommendations.
During
a later lecture period the groups met and discussed their preliminary
protocol
asking for guidance as needed.
As a
group home-work assignment they wrote the laboratory hand-out for their
exercise. They handed in a
first
draft of their experiment about a month before the student
presentations.
The drafts were returned to the groups with suggestions for
improvements.
The students were responsible for testing and revising their
experimental
protocol before they presented it to the class.
In order to test their experimental design they first prepared
solutions
(based on their own calculations) and set up equipment (including cleaning
sufficient glassware for the entire class).
Some of the experiments required more complicated advance preparation
like isolating particular cell fractions to be used later by the class.
These
groups spent additional time in the lab preparing their material. The final draft of their laboratory hand-out was due one
week
before their presentation to allow time for the campus print shop to make
copies.
The lecture
periods devoted to planning the experiments were interspersed with more
traditional lectures during the first eight weeks of the semester.
Throughout the course lecture topics included basic chemistry of
biological molecules, intracellular protein sorting and transport, cellular
metabolism, the cytoskeleton and cell movement, the plasma membrane and
molecular transport, endocytosis, and the extracellular matrix.
The four
student groups designed their experiments using their earlier experience
with
cellular fractionation, enzymatic assays, and the measurement of metabolic
rate
and their knowledge of protein structure, factors that effect enzymatic
activity, lipid biochemistry, and the structure and function of lysosomes
and
mitochondria. The four original
student-designed experiments were:
1. “Quantification of Mitochondrial Levels in
Cardiac and Skeletal Muscles”, a marker enzyme assay (succinate
dehydrogenase)
used to compare mitochondrial abundance in white skeletal muscle, red
skeletal
muscle, and cardiac muscle (all dissected from chicken).
2. “The Effects of Caffeine on Mouse
Metabolism”, an investigation of caffeine as a metabolic stimulant in
mice.
3. “The Breakdown of Triglycerides”, an
investigation of lysosomal lipase from chicken liver.
4. “A Study of Hemoglobin and Iron”, an
investigation of changes that occur when defibrinated blood is stored longer
than its shelf-life.
The grade
for
the laboratory portion of the course was based on three quizzes and the
presentation of their own experiment to the class.
The quizzes covered their understanding of all of the laboratory
exercises performed during the semester including the student-led
experiments. Each component was worth 25 % of their grade.
At the
conclusion of the course I asked for feedback regarding this
experience.
All responses were positive.
Excerpts
from some selected responses follow:
“It
was fun to see each other’s preference in subject and this added to a
diversity in lab.”
“It
has given me the experience of designing an experiment, testing it, and
writing
up a protocol. It requires me to think about what it is that I am doing, as
opposed to just doing it.”
“It
made us think about aspects of experiments that we never really do.”
“It
is a lot of work preparing solutions, ordering materials, designing and
running
the lab and then presenting it.”
“Creating
and performing an experiment makes each student who created it highly
responsible... Because so much time was involved, results mean so much
more.”
“I
felt that designing a lab experiment allowed me to experience what research
would be like. It was good for watching a thought develop from beginning to
finding an answer.”
“Students
tend to learn more from this type of experience.”
“It
gives the students a chance to teach something they want to do.”
“It
confirmed that I never want to teach, but now I can appreciate or
understand more about what it takes to do a lab in class.”
“It
helped bring together a lot of the class experiences I have had in this
major.”
It seems
that
this activity has provided an informal “capstone experience” for the senior
science majors in this cell physiology class. The level of student
enthusiasm
was extremely high. Many of the
student responses encouraged me to continue with this exercise while
allowing
more time for the planning and preparation stage.