Page 1 of 1

FL 2 CP #15

Posted: Fri Jun 07, 2019 12:27 pm
by z3lan
We know from the passage that aromatic side chains absorb at 200 nm, and peptide bonds absorb at about 300 nm. Both the aromatic side chain and the peptide bond are hit by the same photons. Since the peptide bond absorbs at a higher wavelength, by E = hc/lambda, it ought to be absorbing photons of lower energy. It therefore ought to have an excited energy closer to the ground state, leading us to answer choice D.

What's wrong with my logic?

Re: FL 2 CP #15

Posted: Sat Jun 08, 2019 3:35 pm
by NS_Tutor_Mathias
Your logic is airtight, but your givens are backwards: The passage states that aromatic side chains absorb in the 250-290nm region and peptide bonds in the 190-250nm region. Therefore B!

Props for demonstrating your reasoning here - this is always an excellent way to ask a question: It solidifies your understanding as you're explaining what you did, and makes it easy to zero in on where exactly you stumbled.

Re: FL 2 CP #15

Posted: Sun Jun 09, 2019 10:23 am
by z3lan
hahaha lol that would do it... thanks!