So why is it in biology 1001 H2O is not considered a product of glycolysis?
H2O not considered a product of Glycolysis?
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because H2O isn't a byproduct of glycolysis. H2O is a byproduct of the Krebs cycle. it's made in one of the last steps in the Krebs cycle when O2 serves as the last electron carrier and is reduced to O^-2 to combine with H+ to form H2O.
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Got the right idea, just it's not the Kreb cycle but rather tha electron transport chain. Kreb/tricarboxylic acid/citric acid cycle produces NADH, FADH2, GTP, and CO2.
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Water is a product of aerobic respiration. If an organism only uses glycolysis (no TCA or ETC), no water is produced.
Water is produced in the 9th step of glycolysis from 2 phosphoglycerate to pyruvate...from my biochem book also on wiki if you want to look. http://en.wikipedia.org/wiki/Glycolysis
1001 says NADH as product which is a cosubstrate...
I know both of those happens so I choose water as the more logical between those 2
1001 says NADH as product which is a cosubstrate...
I know both of those happens so I choose water as the more logical between those 2
My book also says that it goes from 3-phosphoglycerate (PGA) to phosphoenolpyruvate (PEP) by removal of water during glycolysis. Water is also a product of the ETS but not the Kreb's Cycle.
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So maybe that's just too detailed for the MCAT? Dunno...
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The important connection for the MCAT, or for anything else concerning glycolysis, is the production of NADH which is then used in the ETC if it is an aerobic organism, and if it is not an aerobic organism or not an aerobic condiction then it must be converted back to NAD+ either by fermentation or the production of lactic acid otherwise the whole process stops and glycolysis cannot occur, as NAD+ is a necessary cofactor.
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oh, right. my fault.
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the main focus for glycolysis for the MCAT would be knowing the investment of 2 ATPs per mole of glucose and getting 2x pyruvate as product. As well as 2 NADH and 4 ATPs so net from glycolysis is 2x pyruvate and 6 ATPS.
Energetics are as follows
-2 ATP investment
+4 ATP (2NADH = 2ATPS each)
+4 ATP
Net ATP production through glycolysis per mole of glucose = 6 ATPs
I don't think we usually consider the water from the Dehydration step in glysolysis as a product, at least we didn't cover that in my Biochemistry class.
I have seen some of the Enzyme names come up in some MCAT practice tests, but they are the easy ones like Hexokinase, Phosphfructomutase, Phosphofructokinase etc.
Energetics are as follows
-2 ATP investment
+4 ATP (2NADH = 2ATPS each)
+4 ATP
Net ATP production through glycolysis per mole of glucose = 6 ATPs
I don't think we usually consider the water from the Dehydration step in glysolysis as a product, at least we didn't cover that in my Biochemistry class.
I have seen some of the Enzyme names come up in some MCAT practice tests, but they are the easy ones like Hexokinase, Phosphfructomutase, Phosphofructokinase etc.
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This is false. NADH is used for the production of ATP in the ETC, and even there it is 3 ATP per NADH and 2 ATP per FADH2. If this is an anaerobic organism or tissue under anaerobic conditions, the 2 NADH's are converted back to NAD+.
Either way, you only net 2 ATP from glycolysis. The other ATP production from NADH is through donating H in the ETC, but then you end up in a game of semantics there, where well those ATP aren't technically created during glycolysis however they stem from products of glycolysis. What is important for the MCAT is that glycolysis nets 2 ATP. 4 ATP created in the payoff phase - 2 ATP invested in preparation = 2 net ATP.
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You are right, almost. 2-phosoglycerate catalyzed by Enolase to create the double bond between the 3 and 2 carbon of phosphoenolpyruvate. The result is the dehydration of one H20 molecule per substrate. (Pg. 538 Principles of Biochemistry 5th ed, Lehninger)
I don't know why the EK 1001 does not include this.
U know i am kinda shocked with the amount of people in this thread that doesnt not have what i considered as a solid grasp on glycolysis lol x.x ...
It is kind of funny that in the EK MCAT biology they considered H2O as product...
It is kind of funny that in the EK MCAT biology they considered H2O as product...
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ok, i think you meant in "EK MCAT biology they did not consider H2O as product" i was thinking you didn't learn your lesson after we looked it up in textbooks. lol.
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bro I took a cell physiology/biochemistry class where we had to learn this stuff backwards and forwards... we even have to trace radioactive carbons through the different pathways and believe me glycolysis is nothing compared to pathways such as Pentose phosphate pathway. NADH is only worth 2 ATPs in Glycolysis but yes it is worth 3 from the kreb cycle and ETC.
Do you Remember in your book where upon complete oxidation of 1 mole of glucose net ATP production from glycolysis is 36 ATPS?
Here is where it comes from.
6 Net from my previous post through glycolysis. Per glucose, it would be different if you started with F6P or F16BP since you wouldn't count the investments use of ATPs so it could techincally be 7 ATP or 8 ATP through glycolysis. this is assuming that
we get 2x Moles of 3 phosphoglyceraldyhyde and these gets converted to pyruvate. (because technically 1 of these 3 phosphoglyceraldyhyde has to be converted from Dihydroxyacetone phosphate and this could go and make Glycerol, but thats a different story)
now we put pyruvate through pyruvate dehydrogenase complex and kerb cycle. If you go through and count up all the ATP equivalents in GTP FADH2 NADH etc.. you would see that to completely oxidize 1 mole of Pyruvate you would get equivalent of 15 ATP. Now since 1x mole of glucose = 2x mole of pyruvate. You would have 30 ATPs from complete oxidation of 2x pyruvate through the krebs cycle and ETC. that being said.
Glycolysis= 6 ATP and ATP equivalents per mole of glucose
30 ATP from 2x pyruvate through pyruvate dehydrogenase complex Kerb cycle and ETC
= 36 net ATP upon complete oxidation of 1 glucose.
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This is the way I learned it through college. There have been some advancement on it since that says that 30 ATP is produced in (eukaryote) but again these numbers are generally pretty theoretical. (check out the biochem section of TPR book). I seriously don't think that MCAT would try to trip you up on this though. In the TPR book they count cytosolic NADH as 1.5 ATP and matrix NADH = 2.5 ATP.
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It's 2.5 ATP per NADH and 1.5 ATP per FADH2. Those are the correct values; it's not 3 and 2 like a lot of older books say. I don't think we'll need to know this much detail for the MCAT because the number of ATP generated also varies with how the electrons reach the ETC: ie. through the TCA where they enter at NADH dehydrogenase or from the cytosol via GAP dehydrogenase (I think this is the right enzyme; it's been a while since biochem heh).
Edit: The TPR book mentioned by the previous poster has the right idea about the differences in ATP generated when NADH enters the ETC from the cytosol and the matrix.
Edit 2: If anyone is really interested in the reason why 2.5 ATP is generated from NADH (from the matrix) and 1.5 for FADH2 and NADH from cytosol, here it is. If electrons enter from the matrix (ie. via NADH dehydrogenase for example), the entire process transports 10 H+ from the matrix into the intermembrane space. This proton gradient is used to generate ATP via ATP synthase. It takes 3 H+ to travel through ATP synthase and 1 H+ to transport Pi (inorganic phosphate) into the matrix to generate 1 ATP: so, it takes 4 H+ to generate one ATP. If electrons enter via NADH dehydrogenase from within the matrix, 10 H+ are translocated, so 2.5 ATP is generated. If electrons enter from FADH2 or NADH from outside the mitochondria, they bypass the first enzyme (NADH dehydrogenase), which is responsible for translocating 4 H+. Since they bypass the first enzyme of the ETC, only 6 H+ are translocated; this means that only 1.5 ATP is generated from FADH2 and NADH from the cytosol. Hope this helps. This is how much I can remember off the top of my head but I'm almost 100% sure that this is correct. So, the 3 and 2 ATP values are older values that still exist in some literature/textbooks.
Edit: The TPR book mentioned by the previous poster has the right idea about the differences in ATP generated when NADH enters the ETC from the cytosol and the matrix.
Edit 2: If anyone is really interested in the reason why 2.5 ATP is generated from NADH (from the matrix) and 1.5 for FADH2 and NADH from cytosol, here it is. If electrons enter from the matrix (ie. via NADH dehydrogenase for example), the entire process transports 10 H+ from the matrix into the intermembrane space. This proton gradient is used to generate ATP via ATP synthase. It takes 3 H+ to travel through ATP synthase and 1 H+ to transport Pi (inorganic phosphate) into the matrix to generate 1 ATP: so, it takes 4 H+ to generate one ATP. If electrons enter via NADH dehydrogenase from within the matrix, 10 H+ are translocated, so 2.5 ATP is generated. If electrons enter from FADH2 or NADH from outside the mitochondria, they bypass the first enzyme (NADH dehydrogenase), which is responsible for translocating 4 H+. Since they bypass the first enzyme of the ETC, only 6 H+ are translocated; this means that only 1.5 ATP is generated from FADH2 and NADH from the cytosol. Hope this helps. This is how much I can remember off the top of my head but I'm almost 100% sure that this is correct. So, the 3 and 2 ATP values are older values that still exist in some literature/textbooks.
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