Chem Review (Ch 10, pg. 260 Q5)

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931287m
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Joined: Mon Mar 11, 2019 1:43 pm

Chem Review (Ch 10, pg. 260 Q5)

Post by 931287m » Sun Apr 14, 2019 12:13 pm

How do we know the passage is referring to both purines & pyrimidines when it references the modified Urey-Miller experiment producing components of nucleotides? We know the components of a nucleotide include a nitrogenous base, pentose sugar & a phosphate group. Why are purines & pyrimidines together the answer, and phosphate excluded?

Thank you
NS_Tutor_Will
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Re: Chem Review (Ch 10, pg. 260 Q5)

Post by NS_Tutor_Will » Sun Apr 14, 2019 4:16 pm

Thanks for the question!

Phosphate is excluded because there was no phosphorous included in the experiments, so it couldn't possibly end up in the products barring contamination. In the first paragraph, the passage mentions that the experiment included "water, methane, ammonia, and hydrogen gas, sealed in glass flasks, connected by tubes, forming a closed loop." In the next paragraph, they discuss the modified experiments and say some gases were also added to the experiment ("CO2, N2, H2S, and SO2"), but still no phosphorous is included.

In that same paragraph, the author states "Most of the natural amino acids, and components of nucleotides, have been produced in variants of the Urey-Miller experiment" — this is our clue that parts of nucleotides ("components") were produced. We know a whole nucleotide can't be produced because there's no phosphorous, but we have no reason to think that we couldn't produce purines and pyrimidines. It would be unreasonable to think only one type could be made since the passage gives no indication that this would be the case.

I hope this helps!
931287m
Posts: 42
Joined: Mon Mar 11, 2019 1:43 pm

Re: Chem Review (Ch 10, pg. 260 Q5)

Post by 931287m » Mon Apr 15, 2019 9:11 pm

Perfect! Makes sense. Thank you!
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