April 13, 2021, 09:42:42 PM
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##### Biochemistry and Chemical Biology Forum / Which step is NOT part of the proton-translocation process in ATP synthase?
« Last post by Judy on Today at 01:06:37 AM »
Which step is NOT part of the proton-translocation process in ATP synthase?
A) A negatively charged amino acid in each c subunit becomes neutral upon proton binding.
B) A positively charged amino acid in the a subunit forms an ion pair with a charged amino acid in a subunit.
C) deprotonated c subunits are able to interact only with the a  subunit.
D) An arginine in the a subunit is reversibly protonated and deprotonated in each proton binding event.
E) Proton direction is determined by the relative concentrations of protons on either side of the membrane.

I am not quite sure why D is correct. My guess is that arginine being one of the amino acid within ATP synthase can regulate on/off of the enzyme through protonation/deprotonation. Let me know if my thought is reasonable?
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##### Biochemistry and Chemical Biology Forum / Re: Regarding flavoproteins
« Last post by Judy on Yesterday at 10:03:05 PM »
Yes， Thanks for helping.
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##### Undergraduate General Chemistry Forum / Re: Synthesis of silver metal from silver ore
« Last post by Borek on Yesterday at 07:47:37 PM »
you are here long enough to know it is always required
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##### Physical Chemistry Forum / Re: Rate Law for Reversible Reaction Without Reaction Mechanism
« Last post by Borek on Yesterday at 06:58:59 PM »
Assuming reaction

A + B C + D

(and doing several other assumptions) we have forward reaction rate of $k_f[A][ B]$ and reverse reaction rate of $k_r[C][D]$. At equilibrium forward and reverse reaction rates must be identical:

$$k_f[A][ B]=k_r[C][D]$$

hence

$$\frac{k_f}{k_r}=\frac{[C][D]}{[A][ B]}=K$$

This is known as a kinetic approach to equilibrium. As mjc already explained it is quite handwavy.
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##### Physical Chemistry Forum / Re: Rate Law for Reversible Reaction Without Reaction Mechanism
« Last post by RH111 on Yesterday at 05:22:13 PM »

it's a badly posed question to which the only reasonable answer is "there isn't enough information".

What throws me off, is that Option C is exactly that: not enough information. That's the option I went with when taking the test. It seems odd that they'd include that if, in fact, we cannot answer the question without knowing the mechanism. It seems that there must be something we're missing that allows them to come to the conclusion of Option B. After all, the American Chemical Society is a pretty reputable organization.

Also, would you be able to elaborate on the theory behind the kf/kr = KC equation? I'm not sure I understand how/why it works (albeit in only some situations).

Thanks!
RH111
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##### Undergraduate General Chemistry Forum / Re: Multiple choice thermodynamic question
« Last post by Meter on Yesterday at 05:11:34 PM »
The process is always non-feasible at ΔH > 0, ΔS < 0. So the answer is C.
Correct.
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##### Generic Discussion / Re: Will using Propylene Glycol as a solution protect the solute from oxidation?
« Last post by Borek on Yesterday at 12:18:37 PM »
Please clearly state your purpose. This sounds way too close to self-medication for us to feel comfortable with the idea of helping you.
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##### Analytical Chemistry Forum / Re: How to decapsulate a compound out of micelles?
« Last post by jeffmoonchop on Yesterday at 11:51:49 AM »
We use Triton every day to de-encapsulate mRNA in lipid nanoparticles. You will only need a tiny amount, we use 30ul in 3ml cuvette, wont matter much the concentration of particles. Just wear gloves. I read there are alternatives but I'm sure you can google.

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##### Undergraduate General Chemistry Forum / thermodynamics
« Last post by Akhmal on Yesterday at 11:42:32 AM »
For the reaction H2O(g) + Cl2O(g) → 2HCIO(9), you know S rxn and Sosys and S° of HCIO(g) and of H2O(g). Write an expression that can be used to determine Cl2O(g).

i dont understand this question
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##### Physical Chemistry Forum / Re: Rate Law for Reversible Reaction Without Reaction Mechanism
« Last post by Babcock_Hall on Yesterday at 11:36:36 AM »
mjc123,

What is wrong with answer C?  That would have been what I chose.
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