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Bio AQA question for smart people

In the presence of oxygen, respiration yields more ATP per molecule of glucose than it does in the absence of oxygen. Explain why.

I looked at the mark scheme and don’t understand , help needed
Original post by hopefulDocc
In the presence of oxygen, respiration yields more ATP per molecule of glucose than it does in the absence of oxygen. Explain why.

I looked at the mark scheme and don’t understand , help needed


What level is this - A level or undergrad? The answer lies in the difference between aerobic and anaerobic glycolysis, but I can't help you properly until I know what level you're working at.
Original post by Reality Check
What level is this - A level or undergrad? The answer lies in the difference between aerobic and anaerobic glycolysis, but I can't help you properly until I know what level you're working at.

Sorry , A level Biology
Original post by hopefulDocc
Sorry , A level Biology


OK - have you done both aerobic and anaerobic glycolysis?
Look at glycolysis and anerovix resperiation and see their products and intermediate and you'll find your answer. I think with oxygen it can do Krebs cycle and links reaction and the oxidative phosorlasion but without it can't do Krebs cycle or links I THINK
Original post by Reality Check
OK - have you done both aerobic and anaerobic glycolysis?

I have done aerobic glycolysis but not anaerobic ( totally forgot about that)
ik that in anaerobic turns the pyruvates into ethanol and lactate so no ATP formed and thus less yield ? That’s my guess
Original post by hopefulDocc
I have done aerobic glycolysis but not anaerobic ( totally forgot about that)
ik that in anaerobic turns the pyruvates into ethanol and lactate so no ATP formed and thus less yield ? That’s my guess


Yep, you're spot on - you answered that without any help really. :smile:

So, in the presence of oxygen, the product of glycolysis, pyruvate, can be fed into the TCA and via oxidation pass its high energy electrons onto the electron transport chain and generate ATP via oxidative phosphorylation. As you've noted, in the absence of oxygen, glycolysis stops at pyruvate, and this is reduced to either ethanol via acetaldehyde or lactate (which is oxidised back to pyruvate in certain cells, or is used to generate glucose via gluconeogenesis). So the only ATP production in the absence of oxygen, via anaerobic glycolysis, is that which occurs during the oxidation of glucose to pyruvate during glycolysis.

Look up how many molecules of ATP are formed via anaerobic glycolysis compared to aerobic. It's a huge difference.
(edited 5 years ago)
Original post by Reality Check
Yep, you're spot on - you answered that without any help really. :smile:

So, in the presence of oxygen, the product of glycolysis, pyruvate, can be fed into the TCA and via oxidation pass its high energy electrons onto the electron transport chain and generate ATP via oxidative phosphorylation. As you've noted, in the absence of oxygen, glycolysis stops at pyruvate, and this is oxidised to either ethanol via acetaldehyde or lactate (which is oxidised back to pyruvate in certain cells, or is used to generate glucose via gluconeogenesis). So the only ATP production in the absence of oxygen, via anaerobic glycolysis, is that which occurs during the oxidation of glucose to pyruvate during glycolysis.

Look up how many molecules of ATP are formed via anaerobic glycolysis compared to aerobic. It's a huge difference.

You are brilliant ! Thank you so much for taking the time to help.
Original post by hopefulDocc
You are brilliant ! Thank you so much for taking the time to help.


haha - thanks! You're welcome :smile:

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