Cellular Respiration Case Study Answers

INTRODUCTION

The topic of aerobic cellular respiration is peculiarly hard for undergraduate science students to comprehend. For students to fully comprehend aerobic respiration, they must primary hard concepts including reduction/oxidation reactions, thermodynamics, functions of enzymes, and concentration gradients. Novice learners have a broad range of misconceptions that must be overcome in lodge to achieve deep understanding (Songer and Mintzes, 1994). For example, students often associate respiration just with breathing as opposed to the conversion of energy by cells. Furthermore, some of these misconceptions persist later on intensive instruction, and new ones may ascend for experienced biological science students (Songer and Mintzes, 1994).

Many students unfamiliar with cellular respiration seem to get lost in the memorization of details rather than focusing on the overall process and purpose of cellular respiration. An additional difficulty for instructors is that introductory biological science courses normally must serve both majors and nonmajors, sometimes in the same classroom. These students have different expectations and motivations for being in the class, thus making judgments nearly the level of detail to teach difficult for the instructor. Previous experiences pedagogy aerobic cellular respiration solely using a lecture format did non result in the student learning outcomes that we and other instructors desired: primarily, successful application of concepts on exam questions (see Haslam and Treagust, 1987). Based on responses to questions in class and performance on exams, students (both majors and nonmajors) non but had difficulty learning the material but also in placing the concepts into a broader biological context.

We devised an interactive way to teach aerobic cellular respiration to increase educatee comprehension and understanding of biological primal concepts about cellular respiration. The activity presented hither follows an interrupted instance study method. Traditionally, the case study method has been used in the disciplines of law, business, and medicine. Recently, nonetheless, it has been used in science education (Herreid, 1994). The instance study we present is based on an bodily case of rotenone poisoning of a young girl (De Wilde, 1986). Rotenone is a naturally occurring chemical derived from the roots of several tropical and subtropical plants. Information technology inhibits chemiosmosis by interfering with NADH dehydrogenase preventing utilization of NADH every bit a proton and electron donor in the electron transport concatenation (WHO; Extoxnet Pesticide Information Notebook Rotenone, 1996; Rotenone Health and Prophylactic Guide, Number 73).

Using this existent globe story, the example instantly captivates the students' involvement and likewise provides them with an immediate awarding of the subject area. This case tin serve as an alternative to a traditional lecture or laboratory or can supplement existing activities and assignments. We provide the case (in iv sections) along with a preliminary assessment and evaluation of student outcomes at institutions that used the case in undergraduate introductory biology courses.

TEACHING NOTES

Objectives of the Lesson

Describe the purpose and process of cellular respiration including reactants, products, and cellular location of reactions
Explicate how ATP molecules are produced by the electron transport chain
Depict why oxygen is of import in the process of cellular respiration
Clarify a case study and solve problems based on scientific information

Courses and Student Demographics

The example report was used in Principles of Biological science, an introductory class for both majors and nonmajors at the University of North Carolina at Pembroke (UNC-Pembroke). The course met for one two.5-h session each week. The duration of the case study was one full course period. There were 36 students in the form; four were biology majors and 32 were nonmajors. Well-nigh of the students were nontraditional; 29 of the students were older than 22 yr and xvi students had children. More than than 60% of the students were Native American, African American, and Hispanic American. The remainder of the students were Caucasian. The majority of students lived in rural Northward Carolina.

This case report was also used in General Biology, an introductory class for majors and nonmajors at Shaw University. The course met for two, 2.5-hr sessions per calendar week. The duration of the case study was one full class catamenia. There were 54 students; 33 biological science majors, and 21 nonmajors in the class. Fortyfour of the students were freshman, and the average age was 19 yr. Well-nigh students (∼95%) were African American. The rest of the students were Hispanic American and Caucasian. Most students lived in Raleigh, NC.

Preparation for the Case Report

At UNC-Pembroke, cellular respiration was taught in the context of a unit on the "Life of the Prison cell." Prior to the instance study, the students learned near the major types of macromolecules, the names and basic functions of cell organelles, and the special properties of the plasma membrane. At Shaw Academy, this example study was taught during the "Energy" unit. Topics covered in prior class sessions included macromolecules, cell organelles, improvidence and osmosis.

Prior to the start of the case study, the students in each class were given a take-dwelling quiz on how a single glucose molecule is converted into ATP past the jail cell. The quiz was not particularly challenging only required the students to read the textbook. On the quiz, the students were asked to define ATP, ADP, glycolysis, Krebs cycle, the electron transport chain, and electron carriers, describe precisely where in the prison cell glycolysis, the Krebs cycle, and the electron transport concatenation occur, and listing how many ATP, NADH, and FADH₂ are manufactured from a unmarried glucose molecule past glycolysis, the Krebs bicycle, and the electron transport chain.

Educational activity Methods

We presented information to the students every bit an interrupted case report. The students worked in groups of three to four per group through each part of the example.

In Function 1, we introduced the case study as a mystery that the students would solve. We asked the student groups to read Part i of the case and to discuss the answers to the questions. The questions, which were intentionally open-ended, generated enthusiastic and animated discussion. Students brainstormed ways the daughter may have been poisoned by the flea dip. Many of them pointed out the increased susceptibility of children to toxins and the likelihood that she drank or aspirated some of information technology. Some students even recognized the ethical problems of assuasive the child to use the flea dip unattended. Many of the students suspected that rotenone was the crusade of her death. Five minutes into the give-and-take, we told the grade that rotenone was the poison responsible for the death of the girl. We as well provided a brief background about sources of rotenone and its use by humans. This information stimulated an additional 10 min of discussion. The students raised several excellent points, including: Why don't farmers who apply rotenone pesticides get sick? Why does it kill insects only not humans or pets? What purpose does it serve in the plants that produce it? Is rotenone at present banned from flea dip?

Side by side, we presented Part ii of the case study and asked the student groups to answer the question. We wanted the students to determine that the poison affected energy processing in the mitochondria. This question forced the students to call back previous material on the full general categories of organelle part. Near groups had to refer back to their notes or the textbook before answering. All students eventually came to the decision that they needed to focus on mitochondria and cellular respiration.

After Part 2, nosotros interrupted the case to present a twenty minute lecture on energy. The students were told they needed more data to determine exactly how the poisonous substance killed the girl. At UNC-Pembroke, the lecture included the first and second laws of thermodynamics, diffusion and active transport, and an introduction to enzymes. At Shaw University, the instructor explained the major steps of cellular respiration including the location of reactions, the reactants, products and the number of ATP molecules produced at each step. The lecture covered energy, concentration gradients, and enzymes. Multiple illustrations were included in the presentation for visual learners.

Post-obit the lecture, we presented Role 3 of the example study. Students were asked to discuss what step rotenone afflicted. Working in modest groups, the students successfully narrowed down the possibilities to the Krebs Bike or the Electron Ship Chain. They were able to recognize what steps of aerobic cellular respiration occur inside the mitochondria.

The example study was interrupted for a second lecture afterwards the student groups presented their answers to the discussion question in Part three. The duration of the lecture was 30 minutes and included an overview of the Krebs cycle and chemiosmosis. It covered redox reactions, electron carriers and the transfer of free energy by electrons, a review of electronegativity and the importance of oxygen, active transport, and improvidence in chemiosmosis. This lecture built upon the basic material the students had encountered on the have-domicile quiz.

After the lecture, we presented Part 4 of the case study and asked the pupil groups to reply the discussion questions.

The Case:

You're working at the medical examiner's office at San Francisco County Hospital. It has been a especially low-cal day, with merely 1 homicide and a dead chipmunk that you checked over for rabies. The chipmunk didn't have rabies, and you're set to go dwelling. Just as yous're flipping the switch, you lot get a call from your secretarial assistant. "Francesca," he says. "We've got a expressionless child up here that you'll want to look at right abroad. Might be foul play."

Thinking of your four-twelvemonth old daughter waiting for you at home, you grimace. "OK Jon, I'yard heading to the morgue." Performing autopsies on kids is the least favorite part of your job. But y'all are paid to solve medical mysteries, and it looks like y'all've got i here.

In the morgue, you observe the written report from the hospital. Glancing over information technology, y'all notice a narrative of the daughter's last hours and read it carefully:

At ten AM, mother returns from the store to find daughter vomiting, not feeling well, and sleepy. Mother put girl to bed. 10 minutes later, she noticed that the child's breathing became irregular and deadening. She tried to wake her daughter but was not able to do so. The child became comatose. At noon, the girl was admitted to the hospital, with no heartbeat or spontaneous breathing.

A police study states the following:

The parents discovered that the girl had been giving her dog a bath using a flea dip called Fleacide. According to the characterization on the container, Fleacide is an insecticide made of plant material only and appropriate for external employ on animals.

Questions:

Function 1: The Flea Dip

What could have been in the flea dip that killed the girl?
How could a product that is normally harmless to humans and pets take killed the girl?

PART 2: Autopsy Study

The girl died within two hours of kickoff vomiting
Immediate cause of death was hypoxia (lack of oxy gen)
Tissue sections from the kidneys, lungs, thymus, and eye bear witness massive jail cell death
Staining with cellular dyes indicates that the mitochondria inside the affected tissues were damaged

Question:

Given the autopsy report, and recalling your knowledge from your reading well-nigh the functions of cellular organelles, what functions of the jail cell did the Fleacide touch on?

Role 3: ATP Analysis

A more detailed analysis of the cells from the daughter's heart showed that ATP levels were reduced in the mitochondria. ATP levels in the cytoplasm of these cells, yet, were normal. In addition, acetyl-CoenzymeA levels were normal.

Question:

What cellular process (or processes) was impaired by the Fleacide?

Office iv: Subcellular Analysis

Using a new chromatographic applied science developed late final year, you are able to determine the levels of diverse subcellular components in the heart cells. Key highlights of the written report are listed below:

Questions:

Given this new data, what specific cellular process exercise you lot think was afflicted by the Fleacide? Why?
Some wellness food stores sell supplements containing NAD+. If you administered the supplement to the girl, could y'all salve her? Why or why not?
Would artificial respiration or oxygenation relieve the daughter? Why or why not?

The students immediately recognized that the concentrations of NAD⁺ and NADH from the autopsy were very different from normal levels. Although this role of the instance study was difficult for many students, several understood that part of the electron transport chain was inhibited by the rotenone. These students explained the data to other group members with very little input from the teacher. The students raised in-depth give-and-take questions, and ultimately agreed upon the activity of rotenone. The 2nd question generated the most discussion. At outset, many students thought that the imbalance between NAD⁺ and NADH was the primary problem. However, some students before long determined that the imbalance was merely a result of the action of rotenone. These students convinced the others of their view without input from the instructor.

Finally, as a homework activity students at UNC-Pembroke were given the names and characteristics of other poisons that interfere with cellular respiration (due east.yard., arsenate and cyanide) and asked to make up one's mind what other free energy processes they might bear upon (see Illingworth, 2001).

EVALUATION

Effectiveness of the Example Study

Our goal was to assess the effectiveness of using the case study to increment student comprehension and retention of cellular respiration concepts. Nosotros assessed educatee comprehension qualitatively by monitoring the discussions in the student groups and through the level and sophistication of questions the students asked during class. Semiquantitative assessments were made through a written examination and educatee satisfaction was assessed with a brief survey after the implementation of the case study.

Since the case was discussed during class in student groups, pupil-to-student teaching occurred as noted past the instructors. Ordinarily, a student in the group would suggest an respond to his or her respective group and explicate the reasoning and supporting prove for the proposed answer. In response, some students proposed alternative answers to the case questions within the groups. Instructors monitored exact responses within groups and mediated farther discussion by asking questions to the groups that seemed to be off target. Although not all of the students were able to answer the instance study questions initially, most students were able to provide correct answers afterwards group discussions.

In i teacher's grade, students performed improve when taught using the instance study relative to a previous semester in which cellular respiration was taught solely by the lecture method. The level and sophistication of the discussions and students' questions was much higher when the case study was used. In addition, when given very like exam questions, 70% of the case study students answered correctly compared to but 50% of the students who were taught by lecture only.

During the class period following the example study, the students were given an oral and written quiz. The questions reviewed the steps of cellular respiration in detail. As a class do, the students were able to explain orally the steps of cellular respiration including the location of where each reaction occurs, the reactants and products, and the purpose of oxygen in this procedure. A like instance study question was presented to the students on a mid-term exam (Effigy 1). This question asked about a different poison that blocked aerobic cellular respiration in the mitochondria. The students were asked to brand a diagram of cellular respiration including the cellular location and number of ATP molecules produced during each step. The students were given data similar to the toxic flea dip case written report from which they determined where the block in cellular respiration occurred. About lxxx% of the students responded with right answers to this question. Another measure of assessment was a concept map as a last semester projection. The class that did non utilise the case study was not given a concept map assignment. Of the students who used the case study, approximately lxxx% successfully integrated cellular respiration into their concept map, suggesting that they comprehended of import concepts about cellular respiration.

Student Satisfaction

Using a feedback survey, we set out to probe student perceptions and to determine if the students felt that the case study increased their understanding of cellular respiration. In general, the students responded positively to the example study as a learning tool. Later completing the example study, 75% of the students (21 of 28 students polled) felt that they understood the steps of cellular respiration and that the case written report helped them larn concepts more effectively than a traditional lecture (Figure 2). When asked what the most useful part of the activity was for them, students nearly frequently responded with: the discussion, the questions, and the power to use the data in a existent-life situation (Figure 2).

Addressing Pupil Misconceptions

Previous studies have shown that misconceptions about cellular respiration can persist in the minds of students, fifty-fifty subsequently they have been exposed to varied instructional methods (Haslam and Treagust, 1987; Songer and Mintzes, 1994). We observed that prior to education, the vast majority of students associated the discussion respiration solely with breathing. In addition, they were unable to accurately describe how animals apply energy stored in food, or how oxygen is used in this procedure. After educational activity using the case study, most students were able to accurately identify cellular respiration as the conversion of food energy into ATP. Furthermore, their responses on exam questions and in their concept maps suggested that they could explain why oxygen was required for the process.

CONCLUSIONS

We believe that this interrupted case study provides an effective teaching approach that promotes meaningful and connected comprehension of the important concepts related to cellular respiration. The activities are designed to provide students with multiple opportunities to analyze data and utilize it to a real-earth setting. Throughout the exercise, students must employ disquisitional thinking to make plausible models and so incorporate new data into these models. The use of this case study allows students to piece of work in a collaborative surround, does not crave extensive or expensive equipment, tin can exist used in large or small form settings, and tin can be used to teach both biological science majors and nonmajors. The fact that instructors have used this case written report with a diverse and nontraditional student population implies that it is transferable to many settings. In conclusion, this instance study grounds the principles of cellular respiration to in a true-to-life scenario and enhances critical thinking skills that are applicable to any science. This case study provides a low risk, first step for instructors who desire to incorporate more than active learning strategies into their classroom. More formal and quantitative studies are currently existence undertaken to validate the findings of this study and to evaluate the employ of example studies equally agile learning tools to increase improve student learning outcomes.

ANSWERS TO THE Give-and-take QUESTIONS

Part one Questions:

What could have been in the flea-dip that killed the girl?

The rotenone killed the girl. Nosotros did not wait the students to know that rotenone is toxic, only that at that place was a poison in the flea-dip.
How could a production that is normally harmless to humans and pet s have killed the girl?

The girl must have had an unusual exposure to or received an abnormally high dose of the flea-dip. She may have swallowed a big quantity of it or aspirated the flea-dip into her lungs. If she aspirated the flea-dip, the extensive vascularization of the lungs would ensure rapid dispersal of the poison throughout her body.

In improver, the youthfulness of the victim may take contributed to her death. Many pharmaceutical products are tested for safety only in adults. A safe level of exposure to the flea-dip for an adult may non be safe for a child.

Part ii Question:

Given the autopsy written report and recalling your knowledge from medical school of the functions of the cellular organelles, what general functions of the cell did the Fleacide probably touch?

The massive cell death in the kidneys, lungs, thymus, and heart indicate that harm occurred at the cellular level. More specifically, the damage to the mitochondria suggests that aerobic respiration was disrupted.

Part 3 Question:

What cellular process (or processes) was dumb by the Fleacide?

The normal levels of acetyl coenzyme A indicate that glycolysis is functioning normally. The absence of ATP from the mitochondria suggests that either the Krebs acid cycle or the electron transport chain were impaired.

Function 4 Questions:

Given this new information, what specific cellular process exercise you think was affected by the Fleacide?

The low levels of NAD+ and the high levels of NADH indicate that the kickoff pace in the electron ship concatenation was disrupted. Specifically, the function of NADH dehydrogenase (which converts the electron carrier, NADH, to NAD+) was blocked past the Fleacide.
A product sold in health food stores called Inada contains NAD, what if you administered this to the girl. Could you salvage her? Why or why not?

Probably not. The low level of NAD+ in the heart cells is merely a symptom of the poisoning. The real problem is that rotenone prevents the transfer of electrons from NADH to the electron transport concatenation by inactivating NADH dehydrogenase. Thus, adding NAD+ to the cells may ultimately assistance increase the pool of NADH, but it will not restore the function of the electron transport chain.
Would artificial respiration or oxygenation save the girl? Why or why not?

Probably non. The existent problem is that rotenone prevents the transfer of electrons from NADH to the electron ship chain by inactivating NADH dehydrogenase. A greater concentration of oxygen does not solve the defect in the electron ship chain. This question addresses the misconception that students may have between respiration and cellular respiration.

Metabolite	Autopsy Finding	Normal Levels
Glucose	102 μmol	100 μmol
Pyruvate	23 μmol	25 μmol
NAD⁺	six μmol	75 μmol
NADH	383 μmol	50 μmol

ACKNOWLEDGMENTS

The example report was designed and tested while each writer was a swain in the Seeding Postdoctoral Innovators in Research and Education (SPIRE) program. Formulation and teaching of the example written report was supported by the Minority Opportunities in Enquiry Division of National Plant of General Medical Sciences grant GM000678. We give thanks 50. Lerea for comments and suggestions on the manuscript, and W.E. Bollenbacher and the SPIRE fellows for useful give-and-take during the development of the case report.

REFERENCES

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