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Name: ____________________________________________________________ Score: ____/____The Mystery of the Seven Deaths: A Case Study in Cellular RespirationPart I – The SymptomsImagine that you work at the medical examiner’s office for a major metropolitan city. As Chief Medical Officer, you investigate suspicious deaths and provide toxicology services for the county. Unfortunately, it’s been a busy week. In the past five days, seven people have died, all with similar symptoms. It is your job to examine the data and determine the cause of death for these victims.The first was a 12-year-old girl. Her parents said that she was awake in the middle of the night complaining of a stuffy nose and sore throat. They gave her an extra strength Tylenol and sent her back to bed. At 7am the next morning, the parents discovered that the girl had collapsed on the bathroom floor. An ambulance rushed the girl to a nearby hospital, where she was pronounced dead.That same day, paramedics found the second victim unconscious on his kitchen floor after what they thought was an apparent heart attack. Sadly, the second victim’s brother and fiancée also collapsed later that night while the family gathered to mourn his passing. Both had taken Tylenol to help them cope with their loss shortly before collapsing; neither survived.In the next four days, three other similar deaths were reported, all in the same neighborhood and all with similar symptoms.Are these seven deaths related? What is causing these people to die? It is your job to answer these questions before more deaths are reported.Symptoms exhibited by most patients:DizzinessConfusionHeadacheShortness of breath/rapid breathingVomitingMost deaths were very rapid, occurring within a few hours of symptoms.Questions1. What are the similarities or connections between these seven individuals, beyond the fact that they are dead)? 2. What questions would you want to ask the families to further your investigation?3. In your opinion, are these seven deaths connected? Why or why not?Part II – Autopsy ReportOxygen is carried in the blood by hemoglobin contained in red blood cells. The oxygen binds to the iron in hemoglobin in the lungs and remains attached to the hemoglobin until it reaches its destination in the body. At its destination, the oxygen detaches from the hemoglobin and enters the tissues and then the cells, where it is used in the mitochondria in an energy converting process called aerobic cellular respiration.Immediate cause of death was hypoxia. Hypoxia means that the person suffered from a lack of oxygen, or they were suffocated. Tissue sections from heart, lung, kidney, and liver all show massive cell death.Staining with specific dyes showed major mitochondrial damage within the affected tissues.Oxygen levels in the patients’ blood were approximately 110 mm Hg (normal range is 75 – 100 mm Hg).Questions1. Look carefully at the description of how oxygen moves from the atmosphere and is used in the body. Think of all of the places that the process could be disrupted, and make a list of ways that someone could die of hypoxia.2. Recalling your knowledge of the function of organelles, what function of the cells was interrupted in these patients? 3. Analyze the oxygen levels of the victims. Were the levels higher or lower than normal?4. How can you reconcile this observation with the cause of death being hypoxia?Part III – Aerobic Cellular RespirationYou now understand that the hypoxia was not caused by a lack of oxygen entering the body, or being carried by the blood. Since you have narrowed the problem down to a problem within the mitochondria of the victims’ cells, you begin to think about the process of aerobic cellular respiration (which occurs in the mitochondria of cells). During aerobic cellular respiration, oxygen is used in the process of converting the energy stored in glucose and other food molecules into energy in the form of ATP (adenosine triphosphate). ATP is the form of energy used by the cell to perform all of its functions, so without an abundant supply of ATP, the cell will die. There are three reactions within the process of aerobic cellular respiration: glycolysis, the Kreb’s cycle, and the electron transport chain. The products and reactants of each reaction are listed below:ReactionReactants (including electron carriers)Products (including electron carriers)glycolysisglucose, 2 ADP + P, 2 NAD+2 pyruvate, 2 ATP, 2 NADHKreb’s cycle2 pyruvate, 2 ADP + P, 8 NAD+, 2 FAD+6 CO2, 8 NADH, 2 FADH2electron transport chain10 NADH, 30-32 ADP + P, 2 FADH2, 6 O230-32 ATPFurther metabolic panels of the victims revealed the following levels of metabolites used in aerobic cellular respiration.Average Metabolite LevelsMetabolite Average Patient LevelsNormal LevelsGlucose 99 μM100 μMPyruvate 27 μM25 μMNAD+10 μM75 μMNADH400 μM50 μMQuestions1. Knowing that the victims died from hypoxia, which reaction in aerobic cellular respiration was interrupted?2. What explanation can you give for the extreme difference between levels of NAD+ and NADH in the victims vs. normal levels of these compounds?Part IV: What’s Your Poison?101600164084000You are now convinced that you know the cause of death for these victims and quickly report it back to the police as this is a very dangerous situation. After realizing that the electron transport chain was no longer functioning, you started to suspect poisoning and ran a blood test for various poisons that you knew affected the electron transport chain. The test of all seven patients came back positive for cyanide. Cyanide irreversibly binds to the Cytochrome C oxidase of the electron transport chain and prevents the transfer of electrons to oxygen, the final electron acceptor. Oxygen then binds with hydrogen to create water. ??This process is continuous in cells, with ATP constantly being generated and oxygen being used as the final electron acceptor to produce water.Questions1. Given what you now know about the action of cyanide on cellular respiration, explain why the patients died of lack of oxygen while their blood oxygen levels were normal?2. Would artificial respiration or oxygenation have saved these people? Why or why not?3. Looking back at the information you have about the people before they got sick, can you suggest a possible source of the cyanide poisoning? How should public health officials and police respond to this tragedy? ................
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