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Discussion of all aspects of cellular structure, physiology and communication.
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Cellular Respiration

Fri Dec 31, 2010 8:54 am

Hi! I haven't studied this since high school but I've been thinking about it for some reason and I have some questions that I can't seem to figure out the answer to.

1) I know in cellular respiration glucose is eventually converted to ATP which is used by other cellular processes as a source of energy. My first question is why can't glucose be used directly to 'fuel' these other processes. My guess would be that ATP is easier to break down into ADP to release its energy versus the breakdown of glucose.

2) In the absence of oxygen, fermentation takes place in the cells to produce ATP but in a much smaller amount. My second question is that, even though it is much less efficient, why can't humans (for example) survive indefinitely without oxygen by using fermentation to produce the necessary ATP?

3) Regarding the electron transport chain, I understand what's going on but I would kind of like some info on how it's going on. I think these questions have some chemistry involved that's going to fly right over my head but I'll try and understand anything you say.
3a) What causes NADH to be oxidized into NAD+, H+ and 2e-? Is it as simple as the products being at a lower entropy state than the reactant?
3b) How is the energy from the oxidation of NADH to water used in creating the concentration gradient of protons across the mitochondrial membrane? I understand that it is used by proteins to actively transport H+ ions but how are they doing this?
3c) How does ATP synthase actually create ATP from ADP as H+ moves into the mitochondrial matrix?

I was watching a bio video as I was typing this so the initial questions might be stupidly simple while the latter ones might be stupidly complex haha. I'm in second year of a bio major in uni but, due to poor scheduling on my part, I haven't actually studied very much bio yet. This is all just because I'm curious and love biology! Thanks to anyone who even reads my questions and especially thanks to anyone who answers them! :D

Fri Dec 31, 2010 10:53 am

1) the problem is the energy, which you need/get from respective steps.
Also, as you may know, you need first to iniciate the breakdown by activation of glucose by phosphorylation. So, which step of Glc degradation would you like to connect with other metabolism?
Furthermore, if there is no glucose, would you stop all your metabolic processes? Or is it better to use other sources of energy?

2) I know lot of people who wouldn't need any oxygen. But for the rest of us it's important for the brain and also heart. These organs need lot of energy in short time, so they cannot just fermentate pyruvate to lactate.

3b) I think this is not very well known yet. But probably by changes in structure, the affinities of particular amino acid residues change and thus the protons are transported
3c) it does not create ATP. It only closes ADP and phosphate so close, that the ATP is formed. And the H+ movements causing F0 rotation cause the changes of conformation of subunits in F1.

Fri Dec 31, 2010 11:14 am

1) Makes sense.
2) Haha I could probably go for a while without it.
3b) Also makes sense.
3c) Understood the first two sentences. The rest were way over my head :)

Thanks a lot!
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