question from aamc 9 bs

[imapremed]

which of the following compounds is the precursor for the oxygen atoms in the glycolosis intermediates?

ok so i narrowed it down to only glucose... however, i thought that some of the oxygen atoms that are released as co2 come from the atp that was added and what not during the whole glycolosis + krebs... i mean i came across this when i saw that there were more oxygen molecules released through the number of co2 molecules than there were in glucose..


ALSO:
is it true that vasocontriction and vasodilation can occur on arteries, arterioles AND VEINS? wiki says yes but apprently kaplan says no... i believe in wiki so just to confirm is that true?

any ideas. lemme know.

thanks.

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[icecoldstar]

I have no idea what you said in second paragraph, but it's OK, we'll just ignore it.

remember what glycolysis is? It split glucose (6 carbon compound) into two 3-carbon compounds. those 3 carbon compounds are the glycolysis intermediates.

O2 is used for electron transport chain at the end of everything, so that's why O2 is not right answer.

I tried to put everything in simple terms so ppl can understand, but i can elaborate more if you really want to know the details of stupid glycolysis.

 

[imapremed]

I have no idea what you said in second paragraph, but it's OK, we'll just ignore it.

remember what glycolysis is? It split glucose (6 carbon compound) into two 3-carbon compounds. those 3 carbon compounds are the glycolysis intermediates.

O2 is used for electron transport chain at the end of everything, so that's why O2 is not right answer.

I tried to put everything in simple terms so ppl can understand, but i can elaborate more if you really want to know the details of stupid glycolysis.

what im saying is take a look at the products of glycolysis and the the krebs cycle... look at how many co2 there are... and count up the oxygens... those oxygens could not ALL clearly have come from glucose because it has less oxygen per molecule. Also, i saw in the steps for glycolossi that when triose phosphate dehydrogenase adds to glyceraldehyde 3-phosphate there is an oxygen that adds and then in the next step the phosphate leaves with adp BUT the oxygen is left behind... so i guess what im asking is -

where the heck does the extra oxygen from 1 3 biphosphglycerate coem from cuz glyceraldehyde-3-phosphate doesnt have that extra oxygen.

ALSO HELP ME OUT WITH THE 2nd QUESTION AS WELL PLEASE!

THANKS!

 

[wish2bMD]

Here's the answer to your first question-

"The first reaction is the oxidation of glyceraldehyde 3-phosphate at the carbon 1 position (the 4th carbon from glycolysis which is shown in the diagram), in which an aldehyde is converted into a carboxylic acid (ΔG°'=-50 kJ/mol (-12kcal/mol)) and NAD+ is simultaneously reduced endergonically to NADH. The energy released by this highly exergonic oxidation reaction drives the endergonic second reaction (ΔG°'=+50 kJ/mol (+12kcal/mol)), in which a molecule of inorganic phosphate is transferred to the GAP intermediate to form a product with high phosphoryl-transfer potential: 1,3-bisphosphoglycerate (1,3-BPG). This is an example of phosphorylation coupled to oxidation, and the overall reaction is somewhat endergonic (ΔG°'=+6.3 kJ/mol (+1.5)). Energy coupling here is made possible by GAPDH."
From wikipedia.

 

[imapremed]

Here's the answer to your first question-

"The first reaction is the oxidation of glyceraldehyde 3-phosphate at the carbon 1 position (the 4th carbon from glycolysis which is shown in the diagram), in which an aldehyde is converted into a carboxylic acid (ΔG°'=-50 kJ/mol (-12kcal/mol)) and NAD+ is simultaneously reduced endergonically to NADH. The energy released by this highly exergonic oxidation reaction drives the endergonic second reaction (ΔG°'=+50 kJ/mol (+12kcal/mol)), in which a molecule of inorganic phosphate is transferred to the GAP intermediate to form a product with high phosphoryl-transfer potential: 1,3-bisphosphoglycerate (1,3-BPG). This is an example of phosphorylation coupled to oxidation, and the overall reaction is somewhat endergonic (ΔG°'=+6.3 kJ/mol (+1.5)). Energy coupling here is made possible by GAPDH."
From wikipedia.

yeah but so where does that oxygen come from that transforms the aldehyde to the carboxylic acid? its not an oxygen that comes from the glucose itself.. its an external oxygen... it has to be but from where?

 

[tn4596]

well, vein also have smooth muscles so it can prolly vasodilate and vasoconstrict...but not a lot, i just look at campell and reece and they didnt say anything about vein being capable of vasodilation and vasocontriction.
in glycolosis if you talk about the step where G3P get converted to 1-3 biphosphoglycerate, the oxygen comes from a phosphoric acid...idk why you need to know this, it is unlikely they are going to ask this question on the mcat lol...look at bottom http://en.wikipedia.org/wiki/File:Glycolysis.svg

 

[imapremed]

well, vein also have smooth muscles so it can prolly vasodilate and vasoconstrict...but not a lot, i just look at campell and reece and they didnt say anything about vein being capable of vasodilation and vasocontriction.
in glycolosis if you talk about the step where G3P get converted to 1-3 biphosphoglycerate, the oxygen comes from a phosphoric acid...idk why you need to know this, it is unlikely they are going to ask this question on the mcat lol...look at bottom http://en.wikipedia.org/wiki/File:Glycolysis.svg

thanks dude the answer i was looking for. but you see one question on an aamc 9 asked where does the oxygen in the intermediates come from... my guess was exactly what you said but in more general terms (external source) cuz i didnt know exactly. however, that was not a choice, the answer, and i got it right cuz no other answer made sense was glucose. so in reality that question should have read ONE source of the oxygen atoms in the intermediates...

 

[drechie]

EDIT: Actually, can someone just tell me what this question is actually asking? I didnt understand it. I searched online that the answer is A: glucose.