Bio question.. Help!

[_veo_]

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I just started doing the kaplan subject tests and I missed this question:

If 18O-labeled glucose is given to a rat, where will the
label first appear?
A. Exhaled O2
B. Exhaled CO2
C. Exhaled H2O
D. Plasma H2O
E. Intracellular H2O

I thought it would be E, but now I realize it is wrong. However, I can just come up with the right answer-B via process of elimination.. But I was wondering if anyone can give me a real explanation for this? Thanks!

 

[Manyak222]

This is actually a pretty good question. Remembering that glucose breaks down into 2 pyruvates which get decarboxylated, you can see that these CO2's will leave the cell firstvia RBC's after conversion to Carbonic acid, then bicarbonate, and finally back to CO2 to leave the body via exhilation.
Another good question would be if O2 were labeled and given to a rat, where would you see it first?

 

[_veo_]

This is actually a pretty good question. Remembering that glucose breaks down into 2 pyruvates which get decarboxylated, you can see that these CO2's will leave the cell firstvia RBC's after conversion to Carbonic acid, then bicarbonate, and finally back to CO2 to leave the body via exhilation.
Another good question would be if O2 were labeled and given to a rat, where would you see it first?

My guess is E. Intracellular H2O. But I'm not sure 😳

 

[Manyak222]

Exactamundo!!!
not counting the O2 that you will exhale because you cant take in every O2 molecule per breath, this O2 will become the final electron acceptor during ETC, split to make water, and thus be intracellular O2

My guess is E. Intracellular H2O. But I'm not sure 😳

 

[_veo_]

Exactamundo!!!
not counting the O2 that you will exhale because you cant take in every O2 molecule per breath, this O2 will become the final electron acceptor during ETC, split to make water, and thus be intracellular O2

Cool, that was my reasoning too! There's still hope for me 🙂