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Looking for Biology expert: Do yeast undergo fermentation or aerobic respiration???

(TBF you don't need to be a biology expert to answer this lol it's simple, but I'm not too sure)

My class is doing an investigation, a really simple one. Basically, you make a ball of dough using flour, sugar and yeast, and then submerge it in water to see how long it takes for the dough ball to rise to the surface of the water since the yeast respired. Then you increase the mass of yeast, and see how this affects the results.

Now most of my classmates are saying that the yeast undergoes aerobic respiration instead of anaerobic (fermentation), since when you knead the dough ball there is oxygen trapped inside. But in my opinion, it is anaerobic and I thought that I learnt before that yeast would always choose to undergo fermentation and use all the glucose first, then continue with aerobic when the glucose is running out.

Can someone explain to me how exactly the yeast is respiring in this experiment? Are my classmates correct? We need to write a conclusion and all that, and I really don't know which one it is.

If there's anything I didn't clarify about the experiment, please let me know and I'll be more than happy to reply. Thanks for your help and have a good day!
I'm pretty sure they prefer to respire anaerobically, but I'm not 100% sure if there's oxygen there then they won't use it. The majority would be anaerobic anyway I would have thought. Could you write that as some oxygen is present, there could be both going on? An improvement you could suggest is creating a totally anaerobic environment.
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Original post by DanielK1456
I'm pretty sure they prefer to respire anaerobically, but I'm not 100% sure if there's oxygen there then they won't use it. The majority would be anaerobic anyway I would have thought. Could you write that as some oxygen is present, there could be both going on? An improvement you could suggest is creating a totally anaerobic environment.


Idk i dont think that there could be both going on, but thanks for the help!
If there is oxygen present (which in the description of your setup, it is easy to assume there is), the yeast will respire aerobically. In water, there will be an amount of oxygen dissolved so makes an aerobic environment.

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