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Topic: Glucose from CO2  (Read 893 times)

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Offline ScienceDinoswar

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Glucose from CO2
« on: March 17, 2021, 09:50:09 PM »
A worker in a radioisotope laboratory was accidentally exposed to high levels of 14CO2 during a routine experiment.  When tests of the worker were run and analyzed it was discovered that the glucose in his blood contained 14C.

a. Based on what you now know about metabolism, show how 14CO2 can become incorporated into glucose in the worker, being sure to indicate where in glucose the 14C resides (i.e., in which carbons the 14C is found).  You do not need to show every enzymatic transformation, but you do have to show the key steps in a way that clearly demonstrates you understand what is happening.

  • At first I approached this using the Calvin cycle, but realized that wouldn't work as the worker is not a plant (as far as I know). Then I approached drawing the mechanism in terms of CO2 production with ethanol in anaerobic fermentation to go back to acetaldehyde, back to pyruvate, and ultimately forming glucose with the 14C. Is this a possibly acceptable way for the 14CO2 to be incorporated into glucose where the 14C is C3 and C4?

b. Does this unfortunate accident reveal that humans are actually capable of utilizing CO2 for glucose synthesis, enabling us, like plants, to satisfy our metabolic needs simply by inhaling CO2?  Explain.

  • I've written:
    No because gluconeogenesis requires a lot of ATP to make glucose to be able to be used for metabolic needs, but oxygen releases more energy to give ATP for metabolism. Gluconeogenesis would be inefficient and a lot of work to process. This is the one I'm more so confused about explaining why CO2 being inhaled can't just be used like plants in humans.

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