Glycolysis exergonic?

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Glycolysis exergonic?

Post by mutant » Sun Oct 23, 2005 4:28 am

Having a bit of a problem here. Which steps in glycolysis are exergonic? Please explain structurally why these steps are exergonic. Also, when considering the metabolism of pyruvate to carbon dioxide, which steps involve a decarboxylation, and why is this reaction difficult? Which cofactors are used to make it more favorable? ANy response would help me a great deal. Thanks

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Re: Glycolysis exergonic?

Post by zami'87. » Sun Oct 23, 2005 7:58 am

Hey! Yes glycolysis is exergonic.Most energy is converted and stocked in pyruvate and results of glycolysis are 2ATP and 2(NADPH+ H+). Some energy is released as heat.
NADH and FADH2(from glycolysis and Krebs’ cycle are oxidized and electrons are transported through el trans. Chain to oxygen.Energy is released and ATP is produced.
Which steps? Where the product has less energy than reactant like in steps where ATP is produced from ADP and Pi and substrate is oxidized eg.-1,3-biphosphoglycerate to 3-phosphoglycerate and pyruvate.
Pyruvate to acetyl group-There are 3 enzymes(E1,E2,E3). Enzyme E1 decarboxylates (its cofactor thiamine pyrophosphate reacts) pyruvate.E2 transfers acetyl group to CoA. E3 helps in reduction of NAD+ to NADH.
Then in Krebs cycle isocitrate to alpha-ketoglutarate(enzyme isocitrate dehydrogenase),alpha-ketoglutarate to succinyl-CoA(enzyme alpha-ketoglutarate dehydrogenase).

Correct me if I’m wrong :oops: .

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Post by fran008 » Sun Oct 23, 2005 8:15 am

The exergonic steps i.e. those that are the @energy [email protected] portion of glycolysis are

1. Dihydroxyacetone phosphate -> glyceraldehyde 3-phosphate
2. glyceraldehyde 3-phosphate-> 1,3-Biphosphoglycerate
3. 1,3-Biphosphoglycerate-> 3-phosphoglycerate
4. 31,3-Biphosphoglycerate-> 2-phospoglycerate
5. 2- phospoglycerate->phosphoenolpyruvate
6. phosphoenolpyruvate-> pyruvate
In 1. the DAP molecule is rearranged to form G3P molecul

In 2. the two molecules of G3P gain phosphate groups and oxidised, forming two molecules NADH + H+ and two molecules 1,3-Biphosphoglycerate

In 3 the two molecules of BPG transfer phosphate groups to ADP, formind two ATPs and two molecules of 1,3-Biphosphoglycerate

In 4 the phosphate groups on the two 3PGs move, forming two 2-phospoglycerate

In 5 the two molecules of 2PG lose water, becoming two high-enery phosphoenolpyruvates

In 6 finally the two PEPs transfer their phosphates to ADP forming two ATPs and two molecules of pyruvate.

Next question

So decarboxylation happens when pyruvate is converted to acetyl coA, when isocitrate is turned into alpha ketoglutrate when alpha ketoglutrate is turned to succinyl co A. Reason why it is hard i dont know frankly. Im sure someone else can help.

co factors used are NADH

Hope it was of help

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