| Author | 10 Posts |
nadiabarati
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Please let me know in the conversion of glucose to pyruvate, How many ATP produce, if any? according to the pic, 2 ATP is consumed and 2 ATP is produced so it means no ATP production finally??
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| mosaico
Topics: 1
Posts: 4
| | 02/16/06 - 05:42 PM
1 of 1 forum leaders found this post helpful
| #2 |
You have to think that glucose (6 carbons) opens into two molecules after some steps (fructose1-6bp by aldolase), so actually two glycolisis could be going on from the same glucose (remember that DHAP can be converted to glyceraldehyde-3p) So, if you consumed 2 ATP first, before the aldolase reaction, you could tell that your net production of ATP derived from the "substrate level phosphorilation" (enzimes phosphoglycerate kinase and pyruvate kinase) is 2. You could assume too, that under aerobic conditions you produce 2 NADH for each glucose, by the same principle, but the net production of ATP from NADH would depend on the shuttle used (glycerol or malate) to deliver the electrons to the ETC. ...hope this helps.
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| Valine
Forum Newbie
Topics: 2
Posts: 19
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Thanks mosaico, I'm not nadiabarati but it also heped me to understand the ATP production. It is not well explained in Kaplan Notes. you explanaton is great!!!!.
You should sendo your explanation to them!!! it may help a lot of students like me.
I think you're going to do excellent in you exam.
Good luch
Valine
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| mosaico
Topics: 1
Posts: 4
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Hello Valine, thanks for your kind words
Edited by mosaico on 10/03/07 - 08:18 AM
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| DrVirgo
Forum Hero
Topics: 1058
Posts: 3,383
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Hi everyone.
I just figured out this concept recently as well so here is my explanation:
Glycolysis can produce 6-8 ATP/glucose.
Here is how:
1. Glucokinase Rxn: Loss of 1 ATP
2. PFK-1 Rxn: Loss of 1 ATP
3. Phosphoglycerate Kinase: Gain of 2 ATP (by SLP)
4. Pyruvate Kinase: Gain of 2 ATP (by SLP)
(SLP just means that ATP can be produced in the absence of oxygen or mitochondria, so this can occur in anaerobic conditions or in RBC's which have no mito)
So up to now we have a NET GAIN of 2 ATP/glucose
but there is more:
Glycolysis also produces 2NADH/glucose that can be used for ATP production in the mitochondria. The inner membrane is impermeable to NADH, so we need a shuttle to get it in.
As Mosaico stated: The total ATP from aerobic glycolysis will depend on which shuttle is used.
Its important to know:
The Malate shuttle produces 3ATP
The Glycerol phosphate shuttle produces 2ATP.
-If Malate shuttle used, a TOTAL of 8 ATP/glucose will be made in glycolysis.
This means 2 ATP from above SLP + (2NADH in the Malate Shuttle = 6 ATP)
TOTAL = 8ATP/Glucose
-If Glycerol phosphage shuttle is used, a TOTAL of 6 ATP/glucose will be made in glycolysis
This means 2 ATP from above SLP + (2NADH in Glycerol P Shuttle = 4 ATP)
TOTAL = 6 ATP/Glucose
Conclusion: Depending on which shuttle is used, we can gain a net of 6-8 ATP/glucose in Glycolysis.
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| nadiabarati
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thanks a loooot Drvirgo. But I think you wantta write malate shuttle produces 3NADH and glycerol phosphate shuttle produces 2NADH, right? NOT ATP.
thanks again
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| DrVirgo
Forum Hero
Topics: 1058
Posts: 3,383
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Hi Nadia,
No, I'm pretty sure what I said is right... NADH is produced by glycolysis, which then goes to the Shuttles and they make ATP.
Maybe my wording was wrong, so here it is straight out of Kaplan:
-Aerobic glycolysis yields 2ATP/glucose plus 2NADH/glucose.
-Cytoplasmic NADH oxidized using the malate shuttle produces a mitochondrial NADH and yields approximately 3ATP by oxidative phosphorylation.
-Cytoplasmic NADH oxidized by the glycerol phosphate shuttle produces a mitochondrial FADH2 and yields approximately 2 ATP by oxidative phosphorylation.
-The total ATP from Aerobic glycolysis:
---> 8 ATP/ Glucose (Malate Shuttle)
---> 6 ATP/Glucose (Glycerol Phosphate shuttle)
(I hope this clears up any doubts)
___________________
Our greatest glory is not in never falling, but in rising every time we fall.
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| DrVirgo
Forum Hero
Topics: 1058
Posts: 3,383
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Another point that is important is:
-Malate shuttle: NADH gives electrons to Complex I of ETC
-Glycerol P. shuttle: FADH2 gives electrons to Coenzyme Q (second complex) bypassing Complex I
___________________
Our greatest glory is not in never falling, but in rising every time we fall.
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| mosaico
Topics: 1
Posts: 4
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Hello, I think Drvirgo is right,
The NADH (to produce ATP) comes from glycolysis under aerobic conditions (because under anaerobic conditions it will be utilized by lactate dehidrogenase to make lactate, because O2 is needed by cytochrome oxidase (complex IV) in the electron transport chain and it will not work if there is no O2 present)
The problem is that NADH can not enter directly to the Electron transport chain, so it uses the shuttles drvirgo described.
In the Malate shuttle: Oxaloacetate (OAA) is converted to malate (NADH is used) and malate takes the electron inside the mitocondria and when it is converted back to OAA the reaction forms a "new" NADH.
Now, this NADH can deliver its electron to the NADH dehidrogenase and this reaction would produce an electrical gradient that would open the complexes I (itself) III and IV as the electron passes across the chain, to let the 3 protons (H) get out of the mitochondria. This 3 protons would pass across the F0 component of the ATP synthase complex, back into the mitochondria, and the energy would be used by the ATP synthase to phosphorilate ADP using Pi, making 3 ATP
(and its aprox. Because you can not really count how many protons (H) are in the cytoplasm directly from the proton gradient, so it is theory, but you could assume that the net product is 3 ATP)
In the Glycerol Shuttle: the NADH that came from glycolysis would be utilized in the reaction where DHAP is converted to Glycerol-3P, and Glycerol-3P would take the electron to the Glycerol-P Dehydrogenase, which will utilize FADH2 to convert back glycerol-3P to DHAP, and the electron would be delivered to the ETC (FADH2 to FAD reaction), but because Glycerol-P dehidrogenase is located after NADH Dehidrogenase Complex in the chain, the electron delivered would "open" only Complex III and IV and only 2 Protons would be translocated to the cytoplasm, and this 2 protons would pass trough the F0 component of the ATPsynthase back to the mitochondria to give the energy to produce 2 ATP
So finally we get 6 ATP/glucose (glycerol shuttle) or 8ATP/glucose (malate shuttle) Or if we want: We can have also 7 ATP/glucose : 2 ATP directly from glycolysis + 3 ATP from one NADH in malate shuttle + 2 ATP from the "other" NADH in the glycerol shuttle
Edited by mosaico on 02/17/06 - 04:23 PM
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| nadiabarati
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oh thanks a lot Drvirgo and mosaico. It's very kind of you to spend time to make me understand. I got the whole. Thanks again,dears.
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