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Tomorrow is my birthday! PLEASE HELP ME!!

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Tomorrow is my birthday! PLEASE HELP ME!!

Postby binoo » Mon Apr 03, 2006 6:30 am

I have an exam on Tuesday, please help me. Tomorrow is my b-day so please be kind to me. :lol: Thank you so much!
1. During respiration, how much ATP and NADH is generated by glycolysis for every molecule of glucose? Two each??? Anyone has a correct answer?

2. What happens to the FADH2 and NADH in the Krebs Cycle(=Citric Acid Cycle)? I have no idea.

3. What kinds of molecules comprise the electron transport system?
Is it "Flavoprotein, Cytochromes, and Coenzyme Q"??? Anyone???

4. What is the function of the elctron transport system?
I have no idea. I looked through my text, but I don't know the exact function. This is my first biology class in college. Please help me.

5. In fermentation, what happens to the end product of glycolysis?
2 pyruvate + 2 NADH + 2H+ + 2ATP???

THANK YOU!!!!
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Postby Trev » Mon Apr 03, 2006 10:03 am

1. How much ATP and NADH is generated by glycolysis?
For glycolysis: 2 ATP are formed
For Krebs cycle: 36 ATP

2. What happens to the FADH2 and NADH in the Krebs Cycle(=Citric Acid Cycle)?

FADH2 and NADH take part in oxidative phosphorylation (in internal membrane of mitochondrial) => => => H2O

3. What kinds of molecules comprise the electron transport system?
NADH → Complex I → Q (Complex II) → Complex III → cytochrome c → Complex IV → O2

Complex I: NADH, FMN, FeS-proteins (FeS N1-N3)
Complex I removes two electrons from NADH and transfers them to a lipid-soluble carrier, ubiquinone (Q). The reduced product, ubiquinol (QH2) is free to diffuse within the membrane. At the same time, Complex I moves four protons (H+) across the membrane, producing a proton gradient.

Complex II: FDN, FeS-proteins (FeS S1-S3)
Complex II (succinate dehydrogenase) is not a proton pump. It serves to funnel additional electrons into the quinone pool (Q) by removing electrons from succinate and transferring them (via FAD) to Q. Other electron donors (e.g. fatty acids and glycerol 3-phosphate) also funnel electrons into Q (via FAD), again without producing a proton gradient.

Complex III: cytochrome b, cytochrome c1, FeS-Riske protein
Complex III removes in a stepwise fashion two electrons from QH2 and transfers them to two molecules of cytochrome c, a water-soluble electron carrier located on the outer surface of the membrane. At the same time, it moves four protons across the membrane, producing a proton gradient.

Complex IV (cytochrome c oxidase) removes two electrons from two molecules of cytochrome c and transfers them to molecular oxygen, producing H2O. At the same time, it moves two protons across the membrane, producing a proton gradient.

4. What is the function of the elctron transport system?

ETS are biochemical reactions that produce ATP.

5. In fermentation, what happens to the end product of glycolysis?

Glycolysis connects with exchange lipids, polycacharides; synthesis of nucleotides and aminoacids.
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Postby MrMistery » Mon Apr 03, 2006 5:30 pm

Correction on number one:
Glycolysis produces 2 ATP net and 2 NADH.
Krebs cycle produces 1 ATP, 1 FADH2 and 3 NADH molecule for each pyruvate molecule(double for a glucose molecule).

During the electron transport chain, each NADH molecule produces ~3ATP molecules and each FADH2 produces ~2ATP molecules.

Correction on number 2:
They get reduced, and accept electrons and protons. The electrons will fuel the electron transport chain.

Correction on number 4:
The ETC, per se, only pumps protons, as very well said by Trev. It does not make ATP. The ATP is made by the F0F1 ATp-synthetase enzymes that works like a proton pump in reverse.

Correction on number 5:
Fermentation can produce ATP without oxygen, relying only on the 2 net ATP production of glycolisis. But, in order for glycolysis to progress from step 5 to step 6 it needs a free NAD+ molecule to accept the electron and protons.
Fermentation provides a way of recycling NADH molecules. In fermentation, pyruvate accepts the electrons directly(leading to lactic acid) or is first turned into acetaldehyde and accepts the electrons afterwards(alcoholic fermentation) or other cases. In all cases, the result is the same: the NADH are turned back into NAD+ molecules and glycolysis can follow it's path.

@Trev
Very good explanation on number 3.
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Postby mith » Mon Apr 03, 2006 11:00 pm

Happy Birthday :)
Living one day at a time;
Enjoying one moment at a time;
Accepting hardships as the pathway to peace;
~Niebuhr
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Postby pdavis68 » Tue Apr 04, 2006 1:16 pm

Trev wrote:
1. How much ATP and NADH is generated by glycolysis?
For glycolysis: 2 ATP are formed
For Krebs cycle: 36 ATP


As already stated, Krebs only produces 2 ATP per glucose (1 per pyruvate)

I believe the reference to 36 refers to Oxydative Phosphorylation (Electron transport + Chemiosmosis) which produces either 32 or 34 ATP total.

So the total net yield per glucose molecule is a maximum of 38 ATP.

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