2012 USABO Thread

[asteraceae]

I think the information for the table was basically taken straight out of Raven's Biology.

[darksigma]

si, straight out of campbell and ravens bio.

[asteraceae]

We should really start discussing answers now. I kind of want to know how I did

I'll start: Part C, question number 1 asked for the rate, specific rate, and specific rate in terms of the production of ethanol. The first one I believe was 1 mL/min (or whatever the units were), and apparently to find specific rate we had to use PV = nRT.

darksigma, did you do your calculations right in Part C? I completely bombed it because I didn't realize we had to use the ideal gas law. Oh, well... this is why I'm not doing USNCO.

[cadaeibfed]

Typo in question 101. Oops.

I was not a fan of part C.

[gbraing]

I was not a fan of part C either. No wonder, if it was really so dependent on chemistry knowledge - my class won't cover the ideal gas law until May. I remember trying to take the slope for one of those questions. Oh well, live and learn.

cadaeibfed - What was question 101 about?

[onthemoon]

Question: For Part B, there was a question about where gluconeogenesis occurs and I think I put cytosol as an answer.

But I was wondering if the answer could have been BOTH cytosol and mitochondrial matrix...in that case was I supposed to put in both of them in the scantron even though the question did not specify to put ALL of the answers down??? I feel really ambiguous as to putting down multiple answers when the question doesn't require you to....

[asteraceae]

@onthemoon: Same here. I remember there was a question about photoperiodism and which one would cause a long-day to flower, and I wasn't sure whether they wanted multiple answers.

I don't remember what I put for the gluconeogenesis one, but it looks as though the correct answer would be in the cytosol because I'm guessing the interconversion of amino acids and TCA cycle intermediates would be considered more as amino acid metabolism (or at least that's what I'm thinking the test writers would be thinking). Garret's Biochemistry refers to gluconeogenesis specifically as the conversion of lactate, pyruvate, etc. to glucose, so I think cytosol would be the correct answer.

[onthemoon]

thx asteraceae...there were a lot of ambiguous ones...
btw.. can anyone take a reasonable guess on the cutline? it seems like past years it's been near 57% ish...so may be around 120?

[Cocytus]

Aww man...Part C (except for that 1st question) completely screwed me over. I wasn't smart enough to think of using the ideal gas law. There go my chances...

[tigertwist]

Yeah, I knew that we had to use the ideal gas laws on Part C but forgot what they were so I got those wrong. The biochem was very obscure for everyone who didn't read a good biochem textbook. I should have expected it from the Open Exam, which stressed biochem a lot.

[darksigma]

lol, i sorta kind used ideal gas law? i don't remember the question exactly, but i think i had used it to convert mols to liters for the gas...

[darksigma]

@ asteraceae: just based on your username... i assume you destroyed the final set of questions in set B regarding plant classification?

lol, i knew i should've memorized that scheme the night before, but i decided to study other stuff. i know i got 1 of the 3 for sure, but not sure bout the others...

[emblem101]

On Question 1 in Part C couldn't you just have used the little fact that 1 mol of gas at STP is equal to 22.4 liters of gas: in this case it was CO2.

Then you could have looked at the units and converted to the ones that they wanted.

Then for the ethanol part you could see that the ratio of CO@ to ethanol produced is 1 and therefore you could basically use the same process as in the CO2 part of the problem except with a different molecular mass.

[emblem101]

@ cadaeibfed

Is it possible for you to tell us how many points Part C was worth?

[emblem101]

Here are a few questions to get started with.

Which of the following amino acids has an R-group that can "shuttle" hydrogen ions?

I put histidine since it is electrically charged. The other choices were alanine, leucine, valine, and isoleucine