The Story Steve Knox is a hard-working research biochemist. He has been married

Question

The Story

Steve Knox is a hard-working research biochemist. He has been married to his wife Jackie for over eight years. The project he is working on is a continuation of a project he began in graduate school examining metabolic processes in the mitochondria of Xenopus laevis frogs. His technician Leslie is also very devoted to the project and often works late hours on the weekends with Steve.

Late one Saturday evening, Steve and Leslie are alone in the lab trying to finish up an experiment. As a surprise, Jackie has decided to bring Steve and Leslie a late-night snack since both of them have missed dinner. Around 11:30 pm Jackie enters the lab with drinks and brownies. The lights are on but no one seems to be around.

"I wonder where they are," Jackie muses to herself. "Steve? Leslie? I brought you a surprise!"

Turning a corner in the back of the lav, Jackie sees Steve and Leslie involved in a passionate kiss near the hume hood. SHocked, Jackie drops the food onto the floor, making a clatter. Looking equally shocked, Steve and Leslie immediately disentangle themselves and start sputtering excuses and straightening their clothes.

"Hi, honey, uhhh...what are you doing here?" mutters Steve.

Jackie is enraged. She lunges toward Steve, grabbing his shoulders and shaking him. "What are you doing? Don't you love me anymore? I HATE YOU! I HATE YOU!"

Steve suddenly loses his balance and begins to fall. On his way down, he hits his head on the corner of the lab bench, falling unconcious. Jackie screams.

Leslie, meanwhile, has been watching in horror. Seeing Steve on the floor, she fears for her own safety. Jackie might attack her next! Reacting quickly, she grabs a flask of a clear solution sitting on the counter in the hood and tosses the liquid into Jackie's face, and then runs out of the lab.

Early Monday morning, a colleague discovers Steve and Jackie's dead bodies and calls 911. The coroner later releases information about the estimated time of death for the two based on the extent of rigor mortis. Steve, whose body was still warm and barely stiff, is estimated to have died approximately five hours before being discovered. Jackie, whose body was completely cold and stiff, is estimated to have died approximately 30 hours before being discovered.

Questions:

1. Construct a time-line of the events from Saturday evening through Monday morning as described in the story.

2. cellular respiration questions:

- which part of cellular respiration uses 2 ATP and produces 4 ATP per glucose molecule? Where does this set of reactions occur in the cell?

- Which part of cellular respiration produces the most ATP? How does it work?

- Which part of cellular respiration produces the most NADH? How many?

- What molecules are needed to produce ATP by oxidative phosphorylation?

3. In a living organism, what happens to ATP production when there is no oxygen available (anaerobic conditions)?

Explanation / Answer

2. -http://www.uic.edu/classes/bios/bios100/lecturesf04am/lect12.htm -The part of cellular respiration that produces the most ATP is the Electron Transport Chain. The electron transport chain works by ATP synthase. ATP synthase is an important enzyme that provides energy for the cell to use through the synthesis of adenosine triphosphate (ATP). ATP is the most commonly used "energy currency" of cells from most organisms. It is formed from adenosine diphosphate (ADP) and inorganic phosphate (Pi) which releases energy. -The Kreb's cycle produces the most NADH. It produces 3 per turn which translates into 6 per glucose molecule. 3. When no oxygen is present you can not have oxidative phosphorylation because you need the oxygen to accept the 2 electrons at the end of the electron transport chain. No Oxygen = No electron transport chain. Therefore the cell does not go into the Kreb's cycle either when it senses low oxygen levels because it eventually hits a "dead end" in the electron transport chain. The only other option left is Glycolysis which is truly anerobic. However this only produces 2 ATP vs 38 through the other process. The way it produces ATP anerobically is once it gets to the end of glycolysis NAD gets reduced. However, we have a LIMITED amount of NAD in our cell and as this is our last resort for energy we can not have all of the NAD reduced and need to oxidate it (so that we can keep the process going a little longer) by forming lactic acid. Forming lactic acid allows us to keep using the handful of NADs that we do have giving us a little bit of extra time to find an oxygenated environment. If you continue to exercise/function under anaerobic conditions your overall energy expenditure will be greater than your ATP production and your cells would start to die. Which is why when you strangle someone you're cutting off their oxygen supply and...they die.

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