IB Biology – Year One Unit 7: Lesson 5: Aerobic respiration
AIM: How is pyruvate broken down in the mitochondria to produce carbon dioxide, water and a large yield of ATP?
Warm-up [S] Label the products of anaerobic respiration in the appropriate boxes in the diagram below.
Reaction Reactants
(after glycolysis) Products
(including glycolysis) ATP Yield Cellular Location Aerobic
respiration
Notes on aerobic cellular respiration
No oxygen available
2 pyruvate glucose
This is anaerobic respiration, also known as _________________
Groupwork [G]
Jonathan looks at the diagram above and says “I see 34 total ATP molecules being formed in aerobic respiration.” Charles looks at the diagram and says, “No, there are 36 ATP formed in the process of cellular respiration." Who do you agree with? Justify your choice.
Electron transport
chain AEROBIC
RESPIRATION
6 CO
26 O
26 H
2O
2 H
2O
READ AND ANNOTATE [S]: The Mystery of the Seven Deaths: A case study in cellular respiration The Symptoms
Imagine that you work at the NYC Chief Medical Examiner’s Office. As Chief Medical Officer, you investigate suspicious deaths and provide toxicology services for the city. 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 from Queens. 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 Elmherst 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 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, four 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:
• Dizziness
• Confusion
• Headache
• Shortness of breath/rapid breathing
• Vomiting
Most deaths were very rapid, occurring within a few hours of symptoms.
As you are reviewing the victims’ charts, the coroner comes into your lab, bringing with him the autopsy reports. Here is a summary of what he found.
MEMO
FROM: NYC’S CORONER OFFICE TO: NYC CHIEF MEDICAL EXAMINER RE: AUTOPSY - MYSTERY OF 7 DEATHS
Immediate cause of death was hypoxia (suffocation or lack of oxygen).
• 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).
Individual Questions [S]
1. Are there any similarities or connections between these seven individuals? Name them.
2. Given the data in the autopsy, were there any reports that seemed inconsistent with the immediate cause of death? Name these reports.
IB Biology – Year One Unit 7: Lesson 6: Aerobic respiration case study
You are sitting in the lab flipping through the charts and the autopsy report. As you are reading the charts, you notice a detailed analysis of the damaged cells showing that ATP levels in the mitochondria were very low at the time of death. You begin to suspect a malfunction of a specific cellular metabolic pathway and so you request a more detailed analysis of the sub-cellular components of the affected cells from the autopsy. Soon enough, an e-mail pops up on your laptop. It reads:
FROM: NYC’S CORONER OFFICE TO: NYC CHIEF MEDICAL EXAMINER
RE: SUBCELLULAR METABOLITE ANALYSIS - MYSTERY OF 7 DEATHS
Here is the subcellular metabolite analysis you have requested. The levels of key metabolites are reported below:
Yikes! Don’t worry, this is just an itemized list of specific molecules found in the body and their levels at the time of death.
Groupwork Task [G]
You have a meeting with the chief of police at 7:30 tomorrow morning, and he wants to know what’s behind these deaths. Using your knowledge of cell respiration and the information from the police report and autopsy, develop a hypothesis that could explain the deaths of these patients. You will need to create a representation that clearly shows your hypothesis to present to police chief. This can be a flowchart, annotated diagram, chart, bulleted list, or something else – as long as your representation helps the police staff understand what you think happened and you can use it to justify why your hypothesis explains the death of these 7 victims using data from the case.
Put your work on chart paper. Any individual in your group should be able to explain the thinking behind the work that your group created to the class.
CO
2Lactic acid
Teacher Key
Features of a strong explanation here:
• The glycolysis pathway is in tact, as evidenced by the normal levels of pyruvate being produced.
• The body cells are utilizing the anaerobic pathway rather than the aerobic pathway, as evidenced by the high levels of lactic acid and low levels of carbon dioxide, respectively.
• Anaerobic respiration generates less ATP, so the cells are not releasing adequate energy from their food, causing cell death.
• The most likely explanation is mitochondrial malfunction (specifically, an error in the Krebs Cycle because CO2, which comes from the Krebs Cycle is not being produced but pyruvate is being supplied.)
• The patients had sufficient oxygen (as evidenced by the coroner’s report) but they cannot use it because of the mitochondrial malfunction, so it appears like they are suffocating (you don’t really
“have” oxygen until you have oxygen in your cells!)
• A gas leak or environmental contaminant that damages the mitochondria is a likely culprit based on the details of the case.
Possible extension explanations
• There may be a problem with oxygen transport / diffusion of oxygen from the blood to cells (connections to membrane permeability etc.)
• There is a slightly elevated blood oxygen level; the body may be compensating for the oxygen depletion in the cells by elevating breathing rate to try to fix the problem (homeostasis)
• Lactic acid is a waste product and is toxic in high levels so this could be a cause of the cellular damage as well.
