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Cellular respiration. 3 questions...

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Cellular respiration. 3 questions...

Postby Bioslave » Wed Mar 12, 2008 12:56 am

I am told I should know the follwing

A. How much ATP is produced during fermentation AFTER glucose has been converted to pyruvate.

B. What are the products of fermentation (is there mroe than 3)?

C. What is the role and importance of coenzymes during aerobic respiration


For A I answered 0.

For B, I answered Lactic acid, Hydrogen gas, and Ethanol (I have no idea if there are more than 3 products)

For C, I said coenzyme A is combined with the remaining acetyl to make acetyl CoA which is then fed into the Krebs Cycle.


Are these answeres right or even complete? Any help would be appreciated.
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Postby mith » Wed Mar 12, 2008 2:04 am

B. wrong gas
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Re: Cellular respiration. 3 questions...

Postby MichaelXY » Wed Mar 12, 2008 2:14 am

A. I think 2 ATP's

B. ATP is also produced. For the gas, think of the bubbles in Beer.

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Re: Cellular respiration. 3 questions...

Postby Bioslave » Wed Mar 12, 2008 5:28 am

Thanks for the reply. SO I take it that it's CO2 and not H gas. Is Hydrogen gas produced at all as a product of fermentation in any circumstance?
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Postby MichaelXY » Wed Mar 12, 2008 5:45 am

Here is the chemical equation, according to wiki:
C6H12O6 + 2 Pi + 2 ADP → 2 CH3CH2OH + 2 CO2 + 2 ATP (energy released:118 kJ/mol)
http://en.wikipedia.org/wiki/Fermentati ... emistry%29
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Re: Cellular respiration. 3 questions...

Postby MrMistery » Wed Mar 12, 2008 12:03 pm

Your initial answer to the first question is correct. Two ATP molecules are made, but both of them before the conversion to pyruvate. Have you ever wondered why exactly fermentation occurs? It does so in order to recycle NADH if it cannot be used by the electron transport chain, because glycolysis needs NAD+ in order to take place. Have a look at this picture, showing exactly where ATP synthesis takes place and what happens in fermentation(lactic and alcoholic)
Image

As far as the gas formed from fermentation, it depends on what type of fermentation you are discussing. Most introductory biology books only give lactic acid fermentation and alcoholic fermentation as examples, but there are many more types: mixed acid fermentation(produces both CO2 and H2), butyric acid fermentation(produces H2), caproate fermentation(produces H2), butanol fermentation(produces H2), glyoxylate fermentation(produces H2).

As for the role of coenzymes, I would also include NAD+/NADH and FAD/FADH2 for their critical roles in processes in cellular respiration. Also, there is Coenzyme Q which some do not consider a coenzyme. I say that at least in complex I of the electron transport chain you can list it as a coenzyme.
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Re: Cellular respiration. 3 questions...

Postby MichaelXY » Wed Mar 12, 2008 9:40 pm

Are you sure about that? I got this directly from Campbell amd Reece website.

All cells are able to synthesize ATP via the process of glycolysis. In many cells, if oxygen is not present, pyruvate (pyruvic acid) is metabolized in a process called fermentation. By oxidizing the NADH produced in glycolysis, fermentation regenerates NAD+, which can take part in glycolysis once again to produce more ATP. The net energy gain in fermentation is 2 ATP molecules per molecule of glucose. Fermentation complements glycolysis and makes it possible for ATP to be continually produced in the absence of oxygen.
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Postby mith » Wed Mar 12, 2008 10:16 pm

the net gain is from glycolysis. fermentation produces no atp and is simpy a way to regenerate electron acceptors(producing more atp from this is considered another cycle).
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