Are all the processes (gluconeogenesis, glycogenesis, glycogenolysis, galactose metabolism, fructose metabolism, pentose phosphate pathway etc) all anaerobic? Also, my book states that most of these processes mainly take place in the liver - do we need to know exactly where inside of the cell?
Carbohydrate metabolism
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The first three and the last are all anaerobic mechanisms I believe. The sugars that you asked about are converted to glucose. When you say metabolism of sugars, the gycolysis step will be anaerobic, however, after that it will be aerobic with respect to mammals. I would recommend knowing generally how these processes work. By knowing that you will naturally be able to know where the processes take place. This will help you understand chemical processes of the cell. Understanding is important rather than memorizing facts.
For gluconeogenesis - I know that this process starts with pyruvate and works its way backwards to make glucose. And that pyruvate is coming from either lactate, amino acids or fatty acids - so wouldn't the process be aerobic?
Gluconeogenisis maintains the body's blood sugar because we always need a certain amount of sugar in how blood. GNG (gluconeogenisis) will generate glucose from molecules in metabolism pathways namely, pyruvate, only certain amino acids, and lactate which is oxidized back into pyruvate. GNG has nothing to do with fatty acids! This is important and something to know. Pyruvate releases a lot of energy when it is broken down to acetyl CoA. Acetyl CoA can never become pyruvate again; it is a irreversible step. Fatty acids get broken down into acetyl CoA, therefore, it cannot participate in GNG. Acetyl CoA instead builds up in the mito matrix waiting to participate in the TCA cycle.
Aerobic process "directly" involve molecular oxygen being reduced. It is true that many of these processes indirectly involve O2 or a regulated by O2 - like pyruvate dehydrogenase complex. GNG is not controlled by O2, but rather by the amount of glucose in the blood. A lower amount of glucose in the blood and glycogenolysis not occurring, will definitely promote GNG to turn these precursor metabolism molecules into glucose. You could not say it is an aerobic process because molecule oxygen, O2, is not directly involved.
Electron transport chain is aerobic because it is powered by molecular oxygen, O2. Fermentation is anaerobic because when the ETC cannot keep up with ATP demands, glycolysis must fill the void of ATP. It does this by reducing pyruvate to lactate - this does not involve molecular oxygen.
As for understanding the details of these processes and/or mechanisms. It's good to be aware of them and understand them if they give you a diagram. I'm sure they will connect chemistry and other related concepts to these biological processes. The high energy molecules are important. The regulators are important. The location where this stuff occurs I think is important for understanding. Knowing what molecules can part take in GNG and other processes is important. And finally knowing why GNG needs to occur in the first place along with the other metabolism processes.
Aerobic process "directly" involve molecular oxygen being reduced. It is true that many of these processes indirectly involve O2 or a regulated by O2 - like pyruvate dehydrogenase complex. GNG is not controlled by O2, but rather by the amount of glucose in the blood. A lower amount of glucose in the blood and glycogenolysis not occurring, will definitely promote GNG to turn these precursor metabolism molecules into glucose. You could not say it is an aerobic process because molecule oxygen, O2, is not directly involved.
Electron transport chain is aerobic because it is powered by molecular oxygen, O2. Fermentation is anaerobic because when the ETC cannot keep up with ATP demands, glycolysis must fill the void of ATP. It does this by reducing pyruvate to lactate - this does not involve molecular oxygen.
As for understanding the details of these processes and/or mechanisms. It's good to be aware of them and understand them if they give you a diagram. I'm sure they will connect chemistry and other related concepts to these biological processes. The high energy molecules are important. The regulators are important. The location where this stuff occurs I think is important for understanding. Knowing what molecules can part take in GNG and other processes is important. And finally knowing why GNG needs to occur in the first place along with the other metabolism processes.
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Thats not entirely correct, beta oxidation of odd-chain fatty acids can yield propionyl-CoA which gets converted to succinyl-CoA and then further to oxaloacetate which can fuel Gluconeogenesis. So in a very round about fashion, you can use fatty acids to synthesis glucose.
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Don't forget that glycerol backbone too. If you had some bizarre triacylglycerol with three odd chain fatty acids, you could contribute 3 carbons per fatty acid plus another 3 from the glycerol, for a total of 12 carbons, or two glucose molecules.
Obviously this doesn't happen much, but this theoretical maximum yield is good for winning bar bets. And maybe the obscure MCAT question?
Obviously this doesn't happen much, but this theoretical maximum yield is good for winning bar bets. And maybe the obscure MCAT question?
Does that mean the propionyl CoA actually generates OAA when it is converted to succinyl coA and as that goes through TCA but Acetyl CoA does not which just uses OAA to make citrate and once the TCA is complete, OAA is recycled.
Ratio: 1 propionyl CoA = 1 succinyl coA = 1 OAA = 1 pyruvate = 1/2 glucose - is this right?
So overall, it is possible to use the glycerol part (from all fats) and the propionyl CoA (derived only from the odd length fatty acid chains) in the gluconeogenesis pathway - which takes place in the cytosol of kidneys and liver cells, under anaerobic conditions.
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Not quite, OAA can also be diverted from the Krebs cycle even if it was derived from Acetyl CoA, but this slows the krebs cycle and causes more OAA to be made by Pyruvate Carboxylase. The OAA is actually diverted out of the pathway and converted into PEP and then it follows the normal path to Glucose, not back into Pyruvate first. This is a good image of what I am talking about. http://usmle-review.org/gluconeogenesis.php
