biochem- lecture 1_glycolysis phase 2

chemical logic of step 1 of glycolysis phase 2

energetics of this step

what is oxidized in this step


why is the product a high energy compound
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glyceraldehyde 3-P to 1,3-bisphosphoglycerate

oxidation with one NADH made as a prerequisite for ATP production in the next step
reversible step, endergonic but close to zero

the aldehyde is oxidized to a carboxylic acid with a phosphate
glyceraldehyde-3-P dehydrogenase

because when the phosphate group is removed the product of the removal (3-phosphoglycerate) is extremely stable due to resonance stabilization and so it is extremely favorable to convert to this product in the next step
both reactions are coupled to (1,3-bisphosphoglycerate -> 3-phosphoglycerate), 1,3-bisphosphoglycerate is the intermediate of the reactions so when all are coupled, the overall energy is exergonic and therefore favorable

to keep the endergonic energy low of the two first steps, the product concentrations are kept low to keep them bellow the exergonic value of the last step
when 1,3-bisphosphoglycerate is consumed in step 7, it keeps its concentration low, therefore, the q ratio is kept small which means ΔG will be very negative

this is important because we know multiple reasons why reactions 6 and 7 are coupled, why 1,3-bisphosphoglycerate is the intermediate between glyceraldehyde-3-P and 3-phosphoglycerate. We have mentioned enzyme channelling, coupling of rxns 6 and 7, how concentration levels impact, and how coupling of substrate-level phosphorylation of ATP to step 7 also allows this step to be very exergonic.

Q is another way to explain how reactions 6 and 7 are coupled through the common intermediate
2-phosphoglycerate -> phosphoenolpyruvate enzyme reversibility energetics name of type of reaction --- how is it pulled forwardenolase --- reversible --- endergonic but close to 0 --- dehydration --- pulled forward by having concentration kept lowwhy is it important that 2-phosphoglycerate->phosphoenolpyrovate is a dehydration rxnthe loss of water causes a redistribution of energy so that dephosphorylation releases more energy if dephosphorylation occured on 2-phosphoglycerate, the rxn would be exergonic but not enough to make ATP, but, dephosphorylation of phosphoenolpyruvate does release enough energy to make ATPphosphoenolpyruvate-> pyruvate + ATP: energetics reversibility enzymevery exergonic --- not reversible --- pyruvate kinasestep 10 of glycolysis is two major thingssubstrate level phosphorylation regulation stepdescribe how the step in glycolysis where pyruvate is made is regulatedpyruvate kinase is allosterically inhibited by ATP, acetyl-CoA, and fatty acidsWhy is Phosphoenolpyruvate (PEP) high energy?because its hydrolysis product, pyruvate, is entropically favroablewhy is pyruvate entropically favorable?because pyruvate can convert between its enol and keto form through tautomerizationwhich form of pyruvate is favoredketo formwhat guards the exit gate of glycolysispyruvate kinasewhat inhibits and activates pyruvate kinasepyruvate kinase is allosterically inhibited by ATP, acetyl-CoA and fatty acids it is activated by phosphorylated sugarsthe energy released by phosphoenol hydrolysis to pyruvate releases -61.9kj/mol.why is it so exergonic and what consumes half of it?it is very exergonic because ATP formation consumes 30.5 kj of energy leaving -31.4kj leftafter ATP is made from the free energy released from the formation of pyruvate, what is the extra -31.4 kj of energy used for?constitutes a large driving force pushing the reaction toward ATP synthesiswhat is the net rxn of glycolysisglucose + 2ATP + 2NAD+ + 4ADP + 2Pi-> 2pyruvate + 2ADP + 4ATP + 2NADH + 2H+ + + 2H2Owhat happens when pyruvate is made but there is no oxygen to allow the TCA cycle to consume pyruvatepyruvate can make lactate and ethanol through fermentationwhat organisms have ethanol fermentation and which organisms have lactate fermentationfermentation of ethanol occurs in yeast and fermentation of lactate occurs in animals and other cellslactate fermentation: reversibility enzyme ATP lost energeticsslightly reversible lactate dehydrogenase 1NADH consumed so 2.5 ATP lost and one NAD+ gained very exergonicwhy can lactate fermentation be a good thing?glycolysis produces a little ATP but not a lot. However, it still needs to occur even if aerobic conditions are present. Lactate fermentation produces NAD+ which is required for glycolysis to occurethanol fermentation: what is made enzymes intermediate reversibilityCO2, NAD+, ethanol pyruvate decarboxylase and alcohol dehydrogenase acetaldehyde reversible