Students Design and Present Original Cell Physiology Experiments

 

 

Susan Keys

Biology/Chemistry Department

Springfield College

Springfield, MA 01109

 

 

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.