Destroyer Bio #311

[prsndwg]

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Hi,

can someone help me out with 2009 destroyer bio Q311.. I am absolutely clueless and not even understanding the soln.

Thanks

EDIT:

.................H
NH2-(CH2)4-C-COOH pK1= 2.2 pK2= 9.2 pKR= 10.8
................NH2

Here is the Q:
A biochemist wishes to studyy the effects of pH on conformation. Which stamement is false? why?

a. At pH=7, the amino groups are deprotonated and allow the random coil pf poly-lysine to form
b. At pH=11.5, a stable heliux is likely to form
c. At pH= 1.5, the poly-lysine will likely exist as a random coil
d. At pH=7, the NH3 groups are protonated and cause a destabalizing effect for helix formation


I dont get this at all. please explain it to me.

 

[prsndwg]

bump

 

[alanan84]

When no one answers, that should clue you in to the fact that it's hard to give an answer when you don't know the question. Instead of typing bump, please post the question and we'd be happy to help you out.

 

[razblo]

Could you explain what the question is asking?

I have the 2008 edition and I don't know if problem #311 is the same in that book as it is in mine.

 

[nze82]

The fact that you never mention what the question is asking is why you never get many replies!

 

[prsndwg]

The fact that you never mention what the question is asking is why you never get many replies!

They are hard to draw.. but i ll try to draw them.

 

[prsndwg]

The fact that you never mention what the question is asking is why you never get many replies!

Would you answer it now please

 

[r8 dds]

When you're at a low pH, that means you're still protonated or you still have the hydronium ions still attached. Remember, that when you get pH = pka, you start to lose half of the protons. For lysine, the compound becomes deprotonated at 9.2 (hence, the pK = 9.2).

I believe the question really asks, "At what pH do you have a correct confirmation of lysine?"

At pH of 7, the amino group can't be deprotonated just yet. Thus, choice A is the false statement.

 

[prsndwg]

Thank you.. this is great.
how do you determine the helix or whethyer its coiled or not?

When you're at a low pH, that means you're still protonated or you still have the hydronium ions still attached. Remember, that when you get pH = pka, you start to lose half of the protons. For lysine, the compound becomes deprotonated at 9.2 (hence, the pK = 9.2).

I believe the question really asks, "At what pH do you have a correct confirmation of lysine?"

At pH of 7, the amino group can't be deprotonated just yet. Thus, choice A is the false statement.