A. T. Baines,* M. McVey, B. Rybarczyk, J. T. Thompkid, and also H. R. Wilkins
* Corresponding author: Department of Biology CB#3280Coker Hall University of North Carolina Chapel Hill, NC 27599–3280. E-mail address:ude.cnu.dem
We designed an interrupted situation examine to teach aerobic cellular respiration to significant andnonmajor biology students. The instance is based loosely on a real-life occurrence of rotenonepoisoning. It locations students in the role of a coroner who have to identify the cause ofdeath of the victim. The case is presented to the students in 4 parts. Each component iscomplied with by conversation questions that the students answer in small teams prior to aclasswide conversation. Successive parts of the case provide extra hints to the mysteryand also aid the students focus on the physiological processes connected in aerobicrespiration. Students learn the information forced to resolve the mystery by analysis thecourse textbook prior to course, listening to brief lectures interspersed throughout thecase, and stating the case in tiny groups. The case ends via little team discussionsin which the students are offered the names and also certain molecular targets of various other poisonsof aerobic respiration and also asked to recognize which process (i.e., glycolysis, citric acidcycle, or the electron transport chain) the toxin disrupts.
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Keywords: undergraduate, electron carrier, electron carry chain, power, enzyme, glycolysis, Krebs cycle, mitochondria, thermodynamics, adenosine triphosphate
The topic of aerobic cellular respiration is especially tough for undergraduatescience students to comprehfinish. For students to totally comprehfinish aerobic respiration, theyneed to understand challenging concepts including reduction/oxidation reactions, thermodynamics,functions of enzymes, and also concentration gradients. Novice learners have a broad selection ofmisconceptions that should be conquer in order to achieve deep knowledge (Songer and also Mintzes, 1994 ). For example, students regularly associaterespiration just via breathing as opposed to the convariation of energy by cells.In addition, some of these misconceptions persist after extensive instruction, and new onesmay arise for skilled biology students (Songer and also Mintzes,1994 ).
Many kind of students unacquainted through cellular respiration seem to get lost in the memorization ofdetails quite than focusing on the in its entirety process and function of cellular respiration. Anadded obstacle for instructors is that introductory biology courses frequently mustserve both majors and nonmajors, periodically in the very same classroom. These students havedifferent expectations and motivations for being in the course, for this reason making judgments aboutthe level of information to teach difficult for the instructor. Previous experiences teachingaerobic cellular respiration exclusively using a lecture format did not lead to the studentlearning outcomes that we and various other instructors desired: generally, effective applicationof principles on exam concerns (watch Haslam and Treagust, 1987 ). Basedon responses to concerns in course and also performance on exams, students (both majors andnonmajors) not only had actually difficulty learning the material but also in placing the conceptsright into a wider biological context.
We devised an interactive method to teach aerobic cellular respiration to boost studentcomprehension and understanding of biological crucial ideas about cellular respiration. Thetask presented here adheres to an interrupted case research method. Traditionally, the caseresearch method has actually been supplied in the techniques of regulation, company, and medication. Recently,however, it has been provided in scientific research education (Herreid, 1994 ). Thecase research we present is based on an actual situation of rotenone poisoning of a young girl (DeWilde, 1986). Rotenone is a normally emerging chemical acquired from the roots of severaltropical and also subtropical plants. It inhibits chemiosmosis by interfering with NADHdehydrogenase avoiding utilization of NADH as a proton and also electron donor in the electrondeliver chain (WHO; Extoxnet Pesticide Indevelopment Notebook Rotenone, 1996; RotenoneHealth and also Safety Guide, Number 73).
Using this genuine human being story, the instance instantly captivates the students" interest and also alsoprovides them through an instant application of the subject. This situation deserve to serve as analternate to a typical lecture or laboratory or can supplement existing activities andassignments. We carry out the situation (in 4 sections) along with a preliminary assessment andtestimonial of student outcomes at institutions that supplied the instance in undergraduateintroductory biology courses.
Objectives of the Lesson
Describe the function and procedure of cellular respiration including reactants,commodities, and also cellular location of reactions
Exordinary how ATP molecules are developed by the electron transfer chain
Describe why oxygen is necessary in the process of cellular respiration
Analyze a situation research and resolve troubles based on clinical data
Courses and Student Demographics
The instance examine was provided in Principles of Biology, an introductory course for both majorsand also nonmajors at the University of North Carolina at Pembroke (UNC-Pembroke). The coursemet for one 2.5-h session each week. The duration of the instance examine was one full classperiod. Tbelow were 36 students in the class; four were biology majors and also 32 werenonmajors. Many of the students were nontraditional; 29 of the students were older than 22yr and 16 students had actually youngsters. More than 60% of the students were Native American,Afrideserve to American, and also Hispanic American. The remainder of the students were Caucasian. Themajority of students stayed in rural North Carolina.
This case study was likewise provided in General Biology, an introductory class for majors andnonmajors at Shaw College. The course met for 2, 2.5-hr sessions per week. Theduration of the situation study was one full course duration. There were 54 students; 33 biologymajors, and also 21 nonmajors in the course. Fortyfour of the students were freshmale, and theaverage age was 19 yr. Most students (∼95%) were African Amerideserve to. The remainder ofthe students were Hispanic American and Caucasian. Most students resided in Raleigh, NC.
Preparation for the Case Study
At UNC-Pembroke, cellular respiration was taught in the context of a unit on the“Life of the Cell.” Prior to the instance research, the students learned around thesignificant kinds of macromolecules, the names and standard functions of cell organelles, and thespecial properties of the plasma membrane. At Shaw University, this instance research was taughtin the time of the “Energy” unit. Topics covered in prior course sessions includedmacromolecules, cell organelles, diffusion and also osmosis.
Prior to the begin of the situation research, the students in each class were provided a take-homequiz on just how a solitary glucose molecule is converted right into ATP by the cell. The quiz was notspecifically difficult but required the students to read the textbook. On the quiz, thestudents were asked to specify ATP, ADP, glycolysis, Krebs cycle, the electron transportchain, and electron carriers, define exactly where in the cell glycolysis, the Krebscycle, and the electron carry chain happen, and also list just how many ATP, NADH, andFADH2 are manufactured from a solitary glucose molecule by glycolysis, theKrebs cycle, and also the electron transfer chain.
We presented indevelopment to the students as an interrupted instance examine. The studentsfunctioned in teams of three to 4 per group via each part of the situation.
In Part 1, we presented the situation examine as a secret that the students would certainly fix. Weasked the student teams to check out Part 1 of the situation and to discuss the answers to theconcerns. The inquiries, which were purposely open-ended, generated enthusiastic andanimated conversation. Students brainstormed methods the girl might have actually been poisoned by theflea dip. Many kind of of them stated the boosted susceptibility of children to toxins andthe likelihood that she drank or aspirated some of it. Some students also recognized thehonest concerns of permitting the son to usage the flea dip unattfinished. Many of the studentssuspected that rotenone was the cause of her death. Five minutes into the discussion, wetold the class that rotenone was the poikid responsible for the death of the girl. We alsooffered a brief background around sources of rotenone and also its use by human beings. Thisinformation engendered an additional 10 min of conversation. The students increased severalterrific points, including: Why don"t farmers who use rotenone pesticides gain sick? Whydoes it kill insects yet not human beings or pets? What function does it serve in the plants thatproduce it? Is rotenone currently banned from flea dip?
Next off, we presented Part 2 of the situation study and also asked the student groups to answer thequestion. We wanted the students to identify that the poiboy impacted power processingin the mitochondria. This question required the students to recall previous product on thegeneral categories of organelle feature. Most groups had actually to refer back to their notes orthe textbook before answering. All students eventually came to the conclusion that theyrequired to emphasis on mitochondria and also cellular respiration.
After Part 2, we interrupted the instance to present a twenty minute lecture on power. Thestudents were told they needed more information to recognize exactly how the poiboy killedthe girl. At UNC-Pemdamaged, the lecture consisted of the initially and also second laws ofthermodynamics, diffusion and active transfer, and an advent to enzymes. At ShawCollege, the instructor defined the major procedures of cellular respiration consisting of theplace of reactions, the reactants, products and the variety of ATP molecules developed ateach step. The lecture covered energy, concentration gradients, and enzymes. Multipleillustrations were consisted of in the presentation for visual learners.
Following the lecture, we presented Part 3 of the case examine. Students were asked tocomment on what action rotenone influenced. Working in small groups, the students successfullynarrowed down the possibilities to the Krebs Cycle or the Electron Transport Chain. Theywere able to identify what steps of aerobic cellular respiration happen within themitochondria.
The instance examine was interrupted for a 2nd lecture after the student groups presentedtheir answers to the conversation question in Part 3. The duration of the lecture was 30minutes and also had a summary of the Krebs cycle and also chemiosmosis. It spanned redoxreactions, electron carriers and also the transfer of power by electrons, a review ofelectronegativity and the prominence of oxygen, active move, and diffusion inchemiosmosis. This lecture built upon the basic product the students had encountered onthe take-house quiz.
After the lecture, we presented Part 4 of the case examine and also asked the student groups toanswer the discussion questions.
You"re working at the clinical examiner"s office at San Francisco County Hospital. Ithas been a particularly light day, via just 1 homicide and also a dead chipmunk that youchecked over for rabies. The chipmunk didn"t have actually rabies, and you"re all set to go house.Just as you"re flipping the switch, you get a call from your secretary.“Francesca,” he claims. “We"ve got a dead boy up below that you"lldesire to look at appropriate ameans. Might be foul play.”
Thinking of your four-year old daughter waiting for you at home, you grimace.“OK Jon, I"m heading to the morgue.” Performing autopsies on youngsters is theleast favorite component of your job. But you are paid to settle clinical mysteries, and itlooks choose you"ve obtained one right here.
In the morgue, you find the report from the hospital. Glancing over it, you notice anarrative of the girl"s last hrs and also review it carefully:
At 10 AM, mother retransforms from the save to find girl vomiting, not feeling well, andsleepy. Mother put girl to bed. Ten minutes later, she noticed that the child"sbreathing became irregular and slow. She tried to wake her daughter however was not ableto perform so. The son came to be comatose. At noon, the girl was admitted to the hospital,via no heartbeat or spontaneous breapoint.
A police report states the following:
The parents found that the girl had actually been offering her dog a bath making use of a flea dipcalled Fleacide. According to the label on the container, Fleacide is an insecticidemade of plant material just and proper for outside use on animals.
PART 4: Subcellular Analysis
Using a brand-new chromatographic innovation emerged late last year, you are able to determinethe levels of assorted subcellular components in the heart cells. Key highlights of thereport are listed below:
Given this brand-new information, what specific cellular process carry out you think was affectedby the Fleacide? Why?
Some health food stores offer supplements containing NAD+. If you administered thesupplement to the girl, can you conserve her? Why or why not?
Would man-made respiration or oxygecountry conserve the girl? Why or why not?
The students automatically recognized that the concentrations of NAD+ and NADHfrom the autopsy were very various from normal levels. Although this component of the caseexamine was hard for many kind of students, several understood that part of the electronmove chain was inhibited by the rotenone. These students defined the information toother group members with incredibly little input from the instructor. The students increased in-depthconversation concerns, and also inevitably agreed upon the activity of rotenone. The second questionproduced the many conversation. At first, many type of students assumed that the imbalance betweenNAD+ and NADH was the primary trouble. However, some students quickly determinedthat the imbalance was merely a result of the activity of rotenone. These students convincedthe others of their see without input from the instructor.
Finally, as a homeoccupational task students at UNC-Pemdamaged were offered the names andqualities of various other poisons that interfere via cellular respiration (e.g., arsenateand also cyanide) and asked to recognize what other power processes they can affect (check out Illingworth, 2001 ).
Effectiveness of the Case Study
Our goal was to assess the efficiency of utilizing the instance examine to rise studentcomprehension and also retention of cellular respiration concepts. We assessed studentcomprehension qualitatively by surveillance the discussions in the student groups andvia the level and sophistication of concerns the students asked in the time of course.Semiquantitative assessments were made via a created exam and student satisfactivity wasassessed with a brief survey after the implementation of the instance research.
Since the situation was debated throughout class in student teams, student-to-student teachingdeveloped as noted by the instructors. Typically, a student in the group would certainly indicate ananswer to his or her corresponding group and also define the thinking and also supporting evidencefor the proposed answer. In response, some students proposed different answers to theinstance questions within the teams. Instructors monitored verbal responses within groups andmediated even more conversation by asking questions to the groups that appeared to be offtarget. Although not every one of the students were able to answer the case study questionsinitially, the majority of students were able to carry out correct answers after team discussions.
In one instructor"s course, students perdeveloped much better when taught utilizing the situation studyloved one to a previous semester in which cellular respiration was taught specifically by thelecture approach. The level and also sophistication of the discussions and also students" questionswas much better once the situation study was offered. In addition, when offered exceptionally equivalent examconcerns, 70% of the instance examine students answered effectively compared to just 50% of thestudents that were taught by lecture only.
Throughout the course duration complying with the instance research, the students were provided an dental andcomposed quiz. The questions reregarded the steps of cellular respiration in detail. As aclass exercise, the students were able to define orally the procedures of cellular respirationconsisting of the location of wright here each reactivity occurs, the reactants and also commodities, and also thefunction of oxygen in this procedure. A comparable situation study question was presented to thestudents on a mid-term exam (Figure 1 ). This question asked abouta various poikid that blocked aerobic cellular respiration in the mitochondria. Thestudents were asked to make a diagram of cellular respiration including the cellularlocation and also variety of ATP molecules created in the time of each step. The students were givendata similar to the toxic flea dip case study from which they established where the blockin cellular respiration occurred. About 80% of the students responded via correct answersto this question. Anvarious other meacertain of assessment was a idea map as a final semesterproject. The class that did not usage the instance research was not offered a idea map assignment.Of the students that used the situation research, around 80% properly integratedcellular respiration right into their principle map, arguing that they comprehended importantideas about cellular respiration.
Using a feedback survey, we collection out to probe student perceptions and to recognize if thestudents felt that the instance study enhanced their expertise of cellular respiration.In general, the students responded positively to the instance examine as a finding out tool. Aftercompleting the situation examine, 75% of the students (21 of 28 students polled) felt that theyunderstood the procedures of cellular respiration and that the situation study aided them learnideas more effectively than a standard lecture (Figure 2 ).When asked what the many valuable part of the activity was for them, students mostgenerally responded with: the discussion, the questions, and also the capability to use theindevelopment in a real-life situation (Figure 2 ).
Addressing Student Misconceptions
Previous researches have actually displayed that misconceptions about cellular respiration have the right to persist inthe minds of students, also after they have actually been exposed to differed instructional methods(Haslam and Treagust, 1987 ; Songer and also Mintzes,1994 ). We oboffered that before instruction, the vast majority of studentsassociated the word respiration solely through breapoint. In addition, theywere unable to accurately describe how animals make use of energy stored in food, or howoxygen is offered in this procedure. After instruction making use of the instance study, many students wereable to accurately determine cellular respiration as the conversion of food energy intoATP. Furthermore, their responses on exam questions and also in their principle maps suggestedthat they can describe why oxygen was required for the process.
We believe that this interrupted case examine offers an efficient teaching technique thatpromotes coherent and linked comprehension of the vital ideas connected tocellular respiration. The activities are designed to provide students via multiplemethods to analyze information and also apply it to a real-human being setting. Throughout the exercise,students must employ important thinking to make plausible models and also then incorpoprice newdata into these models. The use of this situation study enables students to work-related in acollaborative atmosphere, does not need considerable or expensive tools, deserve to be used inlarge or little class settings, and also deserve to be supplied to teach both biology majors and also nonmajors.The reality that instructors have actually supplied this instance examine with a varied and also nontraditionalstudent populace suggests that it is transferable to many type of settings. In conclusion, thisinstance examine grounds the ethics of cellular respiration to in a true-to-life scenario andboosts important reasoning skills that are applicable to any kind of clinical discipline. Thissituation examine gives a low risk, first step for instructors who want to incorporate moreactive finding out tactics right into their classroom. More formal and quantitative researches arepresently being undertaken to validay the findings of this study and also to evaluate the usage ofsituation studies as energetic finding out devices to increase enhance student discovering outcomes.
ANSWERS TO THE DISCUSSION QUESTIONS
Part 1 Questions:
What might have been in the flea-dip that killed the girl?
The rotenone eliminated the girl. We did not suppose the students to know thatrotenone is toxic, just that tbelow was a poiboy in the flea-dip.
How could a product that is generally harmless to human beings and also pet s have eliminated thegirl?
The girl need to have had an unusual expocertain to or received an abnormally highdose of the flea-dip. She may have swallowed a huge amount of it or aspiratedthe flea-dip right into her lungs. If she aspirated the flea-dip, the extensivevascularization of the lungs would certainly ensure fast dispersal of the poisonthroughout her body.
In enhancement, the youthfulness of the victim may have actually added to herfatality. Many type of pharmaceutical products are tested for safety just in adults. A safelevel of exposure to the flea-dip for an adult may not be safe for akid.
Part 2 Question:
Given the autopsy report and also recalling your expertise from medical institution of thefunctions of the cellular organelles, what basic functions ofthe cell did the Fleacide more than likely affect?
The substantial cell fatality in the kidneys, lungs, thymus, and heart indicatethat damages occurred at the cellular level. More specifically, the damages to themitochondria suggests that aerobic respiration was disrupted.
Part 3 Question:
What cellular procedure (or processes) was impaired by the Fleacide?
The normal levels of acetyl coenzyme A show that glycolysis isfunctioning usually. The lack of ATP from the mitochondria argues thateither the Krebs acid cycle or the electron transport chain wereimpaired.
Part 4 Questions:
Given this new indevelopment, what specific cellular procedure doyou think was influenced by the Fleacide?
The low levels of NAD+ and the high levels of NADH indicate that the firstaction in the electron deliver chain was disrupted. Specifically, the functionof NADH dehydrogenase (which converts the electron carrier, NADH, to NAD+) wasblocked by the Fleacide.
A product marketed in health food stores called Inada has NAD, what if youadministered this to the girl. Could you conserve her? Why or why not?
Probably not. The low level of NAD+ in the heart cells is merely a symptomof the poisoning. The real difficulty is that rotenone avoids the move ofelectrons from NADH to the electron transport chain by inactivating NADHdehydrogenase. Thus, adding NAD+ to the cells may eventually aid increase thepool of NADH, yet it will not regain the feature of the electron transportchain.
See more: Which Family Contains The Most Reactive Metals In The Periodic Table?
Would artificial respiration or oxygecountry save the girl? Why or why not?
Probably not. The genuine problem is that rotenone stays clear of the carry ofelectrons from NADH to the electron deliver chain by inactivating NADHdehydrogenase. A greater concentration of oxygen does not fix the defect inthe electron deliver chain. This question addresses the misconception thatstudents might have actually in between respiration and cellular respiration.
|Glucose||102 μmol||100 μmol|
|Pyruvate||23 μmol||25 μmol|
|NAD+||6 μmol||75 μmol|
|NADH||383 μmol||50 μmol|